Characterization of erythrocyte parameters during twin pregnancy and risk associated with postpartum hemorrhage: a multicenter retrospective study

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Twin pregnancies are at higher risk of anemia due to increased fetal demand for maternal nutrients and oxygen. In addition, changes in erythrocyte parameters during pregnancy may be specific to twin pregnancy, and these changes may be closely associated with the risk of postpartum hemorrhage (PPH). Therefore, the aim of this study was to explore the specificity of twin pregnancies by comparing the changes in red blood cell (RBC), hemoglobin concentration (Hb), and hematocrit (Hct) at various stages of gestation and to further investigate the relationship between hemoglobin levels and the risk associated with PPH in twin pregnancies. Material and methods: Our study was a multicenter retrospective study involving 4569 twin pregnant women, conducted in 34 hospitals nationwide in China in 2020. First, the levels of RBC, Hb, and Hct were descriptively analyzed to compare whether there were any differences between singleton and twin pregnancies. Second, in twin cases, differences were compared between those at risk for PPH and those not at risk. The subject operating characteristic (ROC) curves and area under the curve (AUC) were calculated for Hb at each stage, and the Hb cutoff value that caused the risk associated with PPH was determined using the risk associated with PPH as the criterion. Finally, the relationship between the duration of low Hb status in twin pregnancies and the risk associated with PPH was explored. Results: (1) RBC, Hb, and Hct were low at all stages of twin pregnancies compared with singleton pregnancies. (2) In twin pregnancy, "low Hb status" at all stages of pregnancy was associated with the risk of PPH. We believe that Hb below 116.5 g/L in the third trimester should be considered a warning against the risk of PPH. (3) The duration of "low hemoglobin status" in twin pregnancy is associated with the risk of PPH. Conclusions: This study shows that the changes in erythrocyte parameters during twin pregnancies are more specific, and the proposed cut-off value of "low Hb status" in twin pregnancy may help to identify the risk of PPH. twin pregnancy red blood cell parameters low hemoglobin state postpartum hemorrhage postpartum anemia Figures Figure 1 Figure 2 Figure 3 Key Message Low hemoglobin status in twin pregnancy is associated with the risk of postpartum hemorrhage Background Twin pregnancy is a high-risk pregnancy state often associated with multiple complications, of which postpartum hemorrhage (PPH) is one of the most serious. Studies have shown that the incidence of PPH is significantly higher in twin pregnancies than in singleton pregnancies [ 1 ] . PPH not only poses a threat to the life and health of the mother but may also cause a decline in quality of life in the long term. Therefore, early identification of pregnant women with high-risk twin pregnancies and appropriate interventions is crucial [ 2 ] . Changes in the hematologic system during pregnancy are a unique physiological state where plasma volume increases disproportionately to red blood cell (RBC) mass, resulting in the possibility of "physiologic anemia of pregnancy" [ 3 – 5 ] . This change is more drastic in high-volume twin pregnancies [ 6 ] , and therefore anemia is more common in twin pregnancies [ 7 , 8 ] . Anemia is strongly associated with the occurrence of PPH [ 9 ] . Hemoglobin (Hb) is an important indicator for assessing maternal anemia status, and in twin pregnancies, low Hb status may be more prevalent, and their impact on the risk of PPH has not been adequately studied. It has been suggested that there may be a correlation between low Hb status and the occurrence of PPH, but the exact cutoff value has not been defined. Therefore, it is important to determine the cut-off value of low Hb status in twin pregnancies to identify the risk associated with PPH. The aim of this study was to explore the peculiarities of twin pregnancies by comparing the changes in RBC, Hb, and hematocrit (Hct) at various stages of gestation. To explore the cut-off values of low Hb status in twin pregnancies and to assess their validity in identifying the risk of PPH. Through this study, we hope to inform clinical practice for better management of twin pregnancies and reduce the incidence of PPH. Methods Study Population and Design: Cases for this retrospective study were obtained from 34 large Chinese hospitals, including Shengjing Hospital of China Medical University. These hospitals were located in seven geographic regions that are traditionally divided into administrative regions in China, covering most of the country (Supplementary material Fig. 1). The different colors in Fig. 1 represent the seven regions of China, and the participating hospitals are mainly divided between the eastern and central regions. Between January and December 2020, a total of 6716 cases were enrolled in this study, of which 5152 were twin cases and 1564 were singleton cases. This study was approved by the Hospital Review Committee of Shengjing Hospital (Ethics Number: 2021PS444K). The ethics committee approved the consent procedure. Supplementary material Fig. 1. Geographical distribution of 34 hospitals across China Data collection: A questionnaire was designed to collect demographic and medical information by interviewing all cases that underwent labor inspection and delivery during the study period. Medical data were extracted from each patient's medical record, including age, gravidity, parity, blood counts at various stages of pregnancy, gestational age at birth, newborn weight, pregnancy complications and co-morbidities (mainly the incidence of hypertensive disorders of pregnancy, thrombocytopenia in pregnancy, etc.), and bleeding during and after delivery. All form fillers at each hospital were trained before the survey was conducted. Each completed questionnaire was verified by a liaison officer. All the compiled data were input independently by two people and then verified by a third person. All cases in the study were eligible for inclusion in the current analysis if they had one or more of the routine blood markers for the first, second, and third trimesters, as well as medical history and pregnancy outcome data. Cases were excluded from this study for one or more of the following reasons: abnormal outcomes, such as miscarriage, intrauterine fetal death, twin pregnancies after single intrauterine fetal demise, and triplet pregnancies. Cases with missing key data (e.g., gestational age at birth, gravidity, parity, postpartum blood counts, and bleeding during labor) were also excluded. Definitions and exclusion criteria: Anemia in pregnancy: according to the diagnostic criteria of WHO guidelines for anemia in pregnancy [ 10 ] , Hb levels below 110 g/L during pregnancy were diagnosed as anemia in pregnancy. PPH: blood loss exceeding 500 mL within 24 hours after childbirth is defined as PPH [ 11 ] . Postpartum anemia is an anemic condition characterized by Hb below 100 g/L within 24–48 hours after childbirth [ 12 , 13 ] . In this study, the risk associated with PPH was defined as the occurrence of either PPH or postpartum anemia following childbirth. Statistical analysis: The SPSS 26.0 statistical package was used for statistical analysis. Differences between the two groups of singleton and twin pregnancies were compared using the chi-square test or the rank-sum test. In order to observe trends in the prevalence of anemia and the levels of RBC, Hb, and Hct at each stage of pregnancy, descriptive analysis was performed using the mean and standard deviation. Differences between the groups with and without PPH risk in twin pregnancy cases were compared using the chi-square test. A logistic regression model was used to test the relationship between erythrocyte parameters and the risk associated with PPH at different stages of twin pregnancy. The feasibility of Hb predicting the risk of PPH was determined using the area under the receiver operating characteristic (ROC) curve, while the Youden index was used to determine the optimal cut-off value of Hb in predicting the risk of PPH at different stages of twin pregnancies. Sensitivity, specificity, positive predictive value, and negative predictive value were used to assess the validity of hemoglobin at different stages of twin pregnancy in the prediction of the risk of PPH. Results Characteristics of the participating population A total of 6716 pregnant women were included in our study. The clinical records of these pregnant women were screened to exclude 261 cases with missing outcome data; 498 cases with conditions affecting blood components and hemorrhagic disorders during pregnancy were excluded. Finally, 5957 gestational cases were statistically analyzed, of which 4569 were twin pregnancies and 1388 were singleton pregnancies (Fig. 2 ). The results showed that a significantly higher proportion of women in the twin group were under 25 years old compared to the singleton group, while the proportion of older (≥ 35 years) women was relatively lower (p < 0.001). The proportion of women under 25 years old was 4.6% in the twin group compared with 3.1% in the singleton group; the proportion of older women was 16.8% in the twin group compared with 25.7% in the singleton group (Table 1 ). In terms of preterm birth, the prevalence of preterm birth was significantly higher in the twin group than in the singleton group, 64.7% versus 6.7%, respectively (p < 0.001). Most of the preterm deliveries in the twin group were concentrated in the 34–37 week period of gestation (47.8%). Regarding newborn weight, the proportion of low birth weight (< 2500 g) was also significantly higher in the twin group than in the singleton group, 55.5% versus 5.2%, respectively (p 0.05). Table 1 Characteristics of the participating population Characteristics All Participants, n (%) Twin pregnancies, n (%) Singleton pregnancies, n (%) p-value n = 5957 n = 4569 (76.7) n = 1388 (23.3) Age at enrollment (years) <25 251(4.2) 208(4.6) 43(3.1) < 0.001 25- 1853(31.1) 1460(32.0) 393(28.3) 30- 2731(45.8) 2136(46.7) 595(42.9) 35- 948(15.9) 652(14.3) 296(21.3) ≥ 40 174(2.9) 113(2.5) 61(4.4) Gravidity 1 2987(50.1) 2266(49.6) 721(51.9) 0.125 ≥ 2 2970(49.9) 2303(50.4) 667(48.1) Parity Primipara 4194(70.4) 3242(71.0) 952(68.6) 0.09 Multipara 1763(29.6) 1327(29.0) 436(31.4) Gestational age at birth (weeks) 28~ 363 (6.1) 346(7.6) 17(1.2) < 0.001 32~ 439 (7.4) 425(9.3) 14(1.0) 34~ 2249 (37.8) 2186(47.8) 63(4.5) ≥ 37 2906 (48.8) 1612(35.3) 1294(93.2) Newborn weight (g) < 1500 283 (4.8) 277(6.1) 6(0.4) < 0.001 1500~ 625 (10.5) 603(13.2) 22(1.6) 2000~ 1699 (28.5) 1655(36.2) 44(3.2) ≥ 2500 3350 (56.2) 2034(44.5) 1316(94.8) Comparison of changes in erythrocyte parameters at various stages of pregnancy in twin versus singleton pregnancies In the present study, a comparison was made between the twin group and the singleton group in terms of the prevalence of anemia, stratified according to the time periods of early, middle, and late pregnancy. The results showed that the prevalence of anemia was significantly higher (p < 0.05 for all) in the twin group compared to the singleton group in the first, second, and third trimesters, as shown in Table 2 . Table 2 Comparison of the prevalence of anemia at various stages of pregnancy in twin versus singleton pregnancies All Participants, n (%) Twin pregnancies, n (%) Singleton pregnancies, n (%) p-value The first trimester No. 2900 1673 1227 < 0.001 Anemia 184 (6.3) 144 (8.6) 40 (3.3) No anemia 2716 (93.7) 1529 (91.4) 1187 (96.7) The second trimester No. 3622 2457 1165 < 0.001 Anemia 1062 (29.3) 872 (35.5) 190 (16.3) No anemia 2560 (70.7) 1585 (64.5) 975 (83.7) The third trimester No. 4680 3556 1124 < 0.001 Anemia 1178 (25.2) 1039 (22.7) 139 (12.4) No anemia 3502 (74.8) 2517 (70.8) 985 (87.6) In the time-series comparison, RBC, Hb, and Hct showed a tendency to decrease initially and then increase slightly during the course of pregnancy, with the lowest levels in the third trimester (Fig. 3 ). Statistical analysis by the rank-sum test revealed statistical differences between the singleton group and the twin group at all three stages of pregnancy (Table 3 ). The mean levels of RBC, Hb, and Hct were lower in the twin group than in the singleton group. These results indicate that the changes in the erythrocyte parameters during twin pregnancies are significantly different from those during singleton pregnancies and have their own special characteristics. Table 3 Comparison of erythrocyte parameters at various stages of pregnancy in twin versus singleton pregnancies The first trimester (Mean SD) The second trimester (Mean SD) The third trimester (Mean SD) Twin pregnancies Singleton pregnancies p-value Twin pregnancies Singleton pregnancies p-value Twin pregnancies Singleton pregnancies p-value n = 1673 n = 1227 n = 2457 n = 1165 n = 3556 n = 1124 Red blood cell (RBC) 4.15 0.45 4.24 0.45 <0.01 3.68 0.42 3.83 1.27 <0.01 3.82 0.41 3.88 0.35 <0.01 Hemoglobin (Hb) 125.62 12.43 129.11 10.42 <0.01 113.56 12.13 118.27 9.46 <0.01 116.32 13.38 120.3 9.71 <0.01 Hematocrit (Hct) 37.08 3.65 38.15 3.87 <0.01 33.97 3.38 35.3 2.95 <0.01 35.09 3.69 35.92 2.91 <0.01 Changes in the erythrocyte parameters during twin pregnancy in relation to the risk associated with PPH In this study, we further analyzed a population of 4569 twin pregnancies and showed that the prevalence of those at risk associated with PPH was 44.9% (2052). Through a chi-square test, we found that there was a significant difference between the group at risk of PPH and the group without risk in parity and newborn weight (p < 0.05). Specifically, the group at risk of PPH demonstrated a higher proportion of primiparous deliveries and a significantly higher mean newborn weight than the group without risk. No significant differences were found between the two groups when comparing age, gravidity, and gestational age at birth (Table 4 ). Table 4 Comparison of characteristics among twin pregnancies with and without the risk of postpartum hemorrhage (PPH) In this study, we conducted a logistic analysis of the risk associated with PPH in twin pregnancies, and univariate analysis revealed that RBC, Hb, and Hct at all stages of pregnancy were significantly correlated with the risk associated with PPH (p < 0.05). The risk associated with PPH decreased significantly with an increase in Hb during pregnancy. Changes in RBC and Hct likewise showed an inverse correlation with the risk of postpartum hemorrhage (Table 5 ). Total Risks associated with postpartum hemorrhage No risk p-value N = 4569 N = 2052 N = 2517 Age at enrollment (Years) 0.168 <25 208(4.6) 96(4.7) 112(4.4) 25- 1460(32.0) 625(30.5) 835(33.2) 30- 2136(46.7) 967(47.1) 1169(46.4) 35- 652(14.3) 316(15.4) 336(13.3) ≥ 40 113(2.5) 48(2.3) 65(2.6) Gravidity 0.707 1 2266(49.6) 1024(49.9) 1242(49.3) ≥ 2 2303(50.4) 1028(50.1) 1275(50.7) Parity 0.015 Primipara 3242(71.0) 1493(72.8) 1749(69.5) Multipara 1327(29.0) 559(27.2) 768(30.5) Gestational age at birth (weeks) 0.105 28~ 346(7.6) 135(6.6) 211(8.4) 32~ 425(9.3) 192(9.4) 233(9.3) 34~ 2186(47.8) 1007(49.1) 1179(46.8) ≥ 37 1612(35.3) 718(35.0) 894(35.5) Newborn weight (g) 0.000 < 1500 277(6.1) 104(5.1) 173(6.9) 1500~ 603(13.2) 231 (11.3) 372 (14.8) 2000~ 1655(36.2) 699 (34.1) 956 (38.0) ≥ 2500 2034(44.5) 1018(49.6) 1016(40.4) Table 4 Comparison of characteristics among twin pregnancies with and without the risk of postpartum hemorrhage (PPH) Total Risks associated with postpartum hemorrhage No risk p-value N = 4569 N = 2052 N = 2517 Age at enrollment (Years) 0.168 <25 208(4.6) 96(4.7) 112(4.4) 25- 1460(32.0) 625(30.5) 835(33.2) 30- 2136(46.7) 967(47.1) 1169(46.4) 35- 652(14.3) 316(15.4) 336(13.3) ≥ 40 113(2.5) 48(2.3) 65(2.6) Gravidity 0.707 1 2266(49.6) 1024(49.9) 1242(49.3) ≥ 2 2303(50.4) 1028(50.1) 1275(50.7) Parity 0.015 Primipara 3242(71.0) 1493(72.8) 1749(69.5) Multipara 1327(29.0) 559(27.2) 768(30.5) Gestational age at birth (weeks) 0.105 28~ 346(7.6) 135(6.6) 211(8.4) 32~ 425(9.3) 192(9.4) 233(9.3) 34~ 2186(47.8) 1007(49.1) 1179(46.8) ≥ 37 1612(35.3) 718(35.0) 894(35.5) Newborn weight (g) 0.000 < 1500 277(6.1) 104(5.1) 173(6.9) 1500~ 603(13.2) 231 (11.3) 372 (14.8) 2000~ 1655(36.2) 699 (34.1) 956 (38.0) ≥ 2500 2034(44.5) 1018(49.6) 1016(40.4) Table 5 Logistics regression analysis of risk associated with postpartum hemorrhage (PPH) Hb is commonly used in clinical practice as a criterion for the diagnosis of anemia; therefore, we compared data on Hb at various stages of pregnancy in twin pregnancies with the occurrence of risk associated with PPH. We assessed the sensitivity and specificity of different Hb cut-offs by plotting ROC curves to find the optimal cut-off value (Table 6 ). The area under the ROC curve (AUC) was 0.56 and 0.58 in the first and second trimesters, respectively, suggesting limited accuracy in predicting the risk of PPH in these two stages. In the third trimester, the AUC was 0.67, suggesting that Hb in the third trimester has a better value in predicting the risk of PPH. Although there were differences in the predictive ability of Hb by stage, the cut-off of Hb in the third trimester showed relatively high sensitivity and specificity. Hb was also found to be associated with the risk associated with PPH in a multifactorial analysis (Table 5 ), suggesting that Hb in the third trimester is an independent risk factor for the risk associated with PPH. More attention should be paid to monitoring Hb in the third trimester in twin pregnancies. Univariate analysis Multivariate analysis B P Exp(B) 95%CI for Exp(B) B P Exp(B) 95%CI for Exp(B) The first trimester Red blood cell (RBC) -0.378 0.001 0.685 0.552 0.851 -0.591 0.030 0.554 0.325 0.944 Hemoglobin (Hb) -0.021 0.000 0.980 0.972 0.987 -0.006 0.599 0.994 0.973 1.016 Hematocrit (Hct) -0.059 0.000 0.943 0.918 0.968 0.017 0.628 1.017 0.949 1.091 The second trimester Red blood cell (RBC) -0.289 0.003 0.749 0.617 0.909 0.077 0.816 1.080 0.564 2.068 Hemoglobin (Hb) -0.024 0.000 0.977 0.970 0.983 0.019 0.199 1.019 0.990 1.050 Hematocrit (Hct) -0.078 0.000 0.925 0.903 0.948 -0.024 0.663 0.977 0.878 1.086 The third trimester Red blood cell (RBC) -0.653 0.000 0.521 0.441 0.615 0.942 0.002 2.566 1.430 4.606 Hemoglobin (Hb) -0.048 0.000 0.953 0.948 0.958 -0.062 0.000 0.940 0.919 0.961 Hematocrit (Hct) -0.156 0.000 0.855 0.838 0.873 0.017 0.680 1.017 0.939 1.101 Table 6 Hemoglobin (Hb) cut-off levels in different stages of twin pregnancies Finally, the level below which a low Hb status was identified was based on a cut-off value that we determined. We further categorized the twin samples with consecutive gestational data into four groups: Group A: no low Hb status throughout the pregnancy; Group B: low Hb status in 1 trimester; Group C: low Hb status in 2 trimesters; and Group D: low Hb status throughout the pregnancy. As shown in Table 7 , as the duration of low Hb status in twin pregnancies increased, the odds ratio (OR) of risk associated with PPH was significantly higher. A similar trend was observed with regard to the risk of postpartum anemia, and the degree of risk of postpartum anemia was higher as the duration increased. In terms of the amount of labor hemorrhage, there was a statistically significant difference in group D, indicating that twin patients who had a low Hb status throughout the pregnancy had a higher risk in terms of the amount of PPH. Cut-off Sensitivity Specificity The area under the ROC curve (AUC) 95% CI p The first trimester 117.5 30.8 81.2 0.56 0.53–0.58 p < 0.01 The second trimester 108.5 39.5 73.6 0.58 0.56–0.60 p < 0.01 The third trimester 116.5 63.9 61.6 0.67 0.65–0.69 p < 0.01 Table 7 The prevalence of adverse postpartum outcomes based on the duration of low hemoglobin (Hb) status N(%) The risk associated with postpartum hemorrhage (PPH) P OR 95%CI The amount of labor hemorrhage P OR 95%CI Postpartum anemia P OR 95%CI N(%) N(%) N(%) Group A 529(39.6%) 220(41.6%) 1 1 1 188(35.5%) 71(13.4) Group B 386(28.9%) 188(48.7%) 0.033 1.334 1.024 1.737 139(36.0%) 0.883 1.021 0.776 1.342 103(26.7) 0.000 2.348 1.677 3.288 Group C 280(21.0%) 157(56.1%) 0.000 1.793 1.338 2.402 98(35.0%) 0.879 0.977 0.721 1.323 106(37.9%) 0.000 3.930 2.776 5.563 Group D 141(10.6%) 106(75.2) 0.000 4.254 2.797 6.470 66(46.8%) 0.015 1.596 1.096 2.324 87(61.7%) 0.000 10.393 6.817 15.843 Discussion The present study found that the changes in the erythrocyte parameters during twin pregnancies are more specialized than in singleton pregnancies. Because of this difference, the management of twin pregnancies should also be different from that of singleton pregnancies. Therefore, the concept of low Hb status is proposed in this study. In twin pregnancies, low Hb status in the third trimester is highly associated with the PPH. Women with twin pregnancies who remain in low Hb status for a prolonged period of time should be more vigilant for PPH and postpartum anemia. By comparing the singleton and twin groups, this study found that the prevalence of anemia in the twin group was significantly higher than that in the singleton group in the first, second, and third trimesters, which is consistent with the findings of previous studies. Twin pregnancies result in a significant increase in maternal demand for iron and other nutrients due to the increase in the number of fetuses, leading to an increase in the incidence of anemia [ 8 ] . In addition, the present study similarly found that the levels of RBC, Hb, and Hct showed a decreasing and then slightly increasing trend with increasing gestational weeks, with the lowest level in the second trimester in both singleton and twin groups. The phenomenon is consistent with previously reported studies [ 14 , 15 ] in the overall population of pregnancy and may be related to the imbalance between the increase in plasma volume and the increase in erythrocyte volume in the second trimester, leading to hemodilution [ 6 ] . Therefore, the diagnostic segmental definition of anemia according to gestational stage is more in line with the changes in the erythrocyte parameters in twin pregnancies. This is consistent with the criteria for the diagnosis of anemia in pregnancy proposed by the American College of Obstetricians and Gynecologists (ACOG) and the British Committee for Standards in Haematology (BCSH). The diagnostic criteria for anemia in pregnancy is consistent [ 16 , 17 ] . Similarly, the Chinese Twin Anemia Group has endorsed this viewpoint and suggested that stage-based diagnosis is more in line with the physiological characteristics of twin pregnancy [ 18 ] . Compared to singleton group, twin group had significantly lower RBC, Hb, and Hct at all stages. This result is consistent with other studies on hematologic system changes in twin pregnancies [ 15 , 19 ] . It further supports the theory of maternal hematologic system changes during twin pregnancies [ 6 ] .The study by Blickstein I et al. also found that the RBC and Hb in twin pregnancies were generally lower than those in singleton pregnancies, a phenomenon that may be related to the increased physiological load associated with twin pregnancies [ 20 ] . The increase in blood volume is more pronounced in women with twin pregnancies, leading to more pronounced hemodilution [ 21 ] . In this study, in order to provide an in-depth analysis of the twin pregnancy population, postpartum anemia was added to the outcome variables along with PPH as the final outcome. The assessment of postpartum blood loss in clinical work is relatively subjective and lacks precision, with many studies proposing that clinical underestimation of postpartum blood loss is common [ 22 , 23 ] , and others suggesting that overestimation of a small amount of hemorrhage and underestimation of a large amount of hemorrhage occur in clinical work [ 24 ] . Postpartum anemia likewise reflects bleeding during delivery [ 12 ] , and in a study by Anger et al. [ 25 ] , it was found that the occurrence of postpartum anemia was common in women with ≥ 1000 ml of blood loss during delivery. Therefore, to improve the accuracy of assessment, the present study added postpartum anemia to PPH as the criterion for determining prognosis. Subsequently, this study compared those at risk of PPH with those not at risk and found significant differences in parity and newborn weight. Specifically, the group at risk for PPH showed a higher proportion of primiparous women, which is consistent with the findings of previous studies that primiparous women may be at higher risk for complications [ 26 ] . The mean weight of the newborns was significantly higher in the group at risk of PPH than in the group without risk. This result may be related to the physiological characteristics of twin pregnancies, which are usually accompanied by higher fetal weights (Wang et al., 2021), which predispose to poor contractile function after uterine overstretching, and larger placental area resulting in greater hemorrhagic area, among others [ 27 ] . Although univariate analysis suggested that changes in the erythrocyte parameters in the first and second trimester were associated with the risk of PPH, a ROC curve was performed that revealed limitations in prediction of the risk associated with PPH at these two stages. In contrast, Hb in the third trimester was a better predictor. Moreover, multifactorial analysis found that Hb in the third trimester was associated with the risk of PPH, indicating that low Hb status in the third trimester was an independent risk factor. This finding is consistent with the findings of Allary et al. [ 28 ] , who also stated that anemia in late pregnancy is an independent risk factor for PPH. In addition, a review by Omotayo et al. [ 9 ] also mentioned that prenatal anemia increases the risk of PPH. All these findings suggest the importance of monitoring Hb in the third trimester to reduce the risk of PPH. Unlike previous studies, this study emphasizes the important role of Hb in a population with twin pregnancies. The novelty of this study is that we proposed the concept of "low Hb status" for the twin pregnancy population. In twin pregnancies, due to the different physiological and pathological manifestations from singleton pregnancies [ 6 ] , even if they are not anemic, higher hemoglobin levels are required to avoid PPH or anemia due to the demands of delivery. The cut-off values in this study are slightly higher than the WHO anemia criteria, which is for the general population, and in the case of twin pregnancies, both blood loss during labor and energy expenditure are higher than in singleton pregnancies. A slightly higher cut-off value would help to minimize complications in twin pregnancies, the cut-off value in this study aligns more closely with real-life needs. Finally, we analyzed the duration of the low Hb status. We found a significant correlation between the duration of the low Hb status and peripartum quantitative blood loss, postpartum anemia, and PPH-related risk. The risk associated with PPH and the risk of postpartum anemia increased significantly with the duration of the low Hb status. With regard to the peripartum quantitative blood loss, the twin pregnancies with the low Hb status throughout the pregnancy had a higher risk of blood loss. Therefore, it is necessary to emphasize and pay attention to the specific blood changes in the twin pregnancy and refine the diagnostic criteria. We believe that this study provides more evidence for the guidance of pregnancy care in the twin pregnancy. This study examined PPH and postpartum anemia as primary outcomes, but the prognostic outcomes of twin pregnancies are multifactorial, including maternal complications [ 29 , 30 ] , the presence of complicated twins [ 31 ] , and neonatal birth status [ 32 ] , among other factors. Therefore, the cut-off value for low Hb status used in this study cannot be used as a diagnostic criterion for anemia in twin pregnancies. The relatively low impact of low Hb status on PPH in the first and second trimesters found in this study may be due to the time gap from delivery, which limits the predictive power of cut-off values in these two stages for the risk associated with PPH. Future studies need to further refine the assessment of the relevant aspects to provide stronger evidence for clinical practice in twin pregnancies. Conclusion The changes in the erythrocyte system during twin pregnancies are more specific, and the cut-off value of "low Hb status" proposed in this paper can help to identify the risks associated with PPH in twin mothers. Abbreviations Declarations Ethics statement This retrospective study was ethically approved by the Research Ethics Committee of Shengjing Hospital affiliated to China Medical University (no. 2021PS444K, Shenyang, China). Approval Date: March 10, 2021.Written informed consent was obtained from individual or guardian participants. All methods were performed in accordance with the relevant guidelines and regulations (Declaration of Helsinki). Consent for publication Not applicable Competing interests The authors declare that they have no competing interests Funding This study was funded by National Key Research and Development Program of China (2023YFC2705900). This study was also funded by Science and Technology Projects of Liaoning Province, China(2021JH2/10300081). Author Contribution JYL analyzed the data, and was a major contributor in writing the manuscript. FX, J L,XY, WQY, XC, HLH, JYH, YZ and CXL participated in collecting data. SWY and JW participated in the revision and quality control of the article. JYL, YZ and CXL participated in the design of the article. All authors have read and approved the manuscript. Acknowledgement The authors thank all participants in 2020 retrospective study of Twin pregnancy anemia group in China Association of Maternal and Child Health Care Professional Committee of twin pregnancy for their dedication and contributions.They thanked Jiajin Hu of China Medical University for his technical support. The hospitals participating in the 2020 retrospective study of the twin anemia group are as follows: Women's Hospital School of Medicine Zhejiang University, The First Affiliated Hospital Of Anhui Medical University, Fujian Provincial Maternity and Children's Hospital, Hunan Provincal Maternal and Child Health Care Hospital, Maternal and Child Health Hospital of Hubei Province, Tongji Medical Colleg, Huazhong University of Science and Technology, Northwest Women’s and Children’s Hospital, Nanjing Drum Tower Hospital, Gansu Provincial Maternity and Child-care Hospital, The International Peace Maternity and Child Health Hospital of The China Welfare Institute, Dalian women and children's Medical Hospital, Kunming City Maternal and Child Health Hospital, Anhui Province Maternity and Child Health Hospital, The First Affiliated Hospital of Zhengzhou University, The First Bethune Hospital of Jilin University, Affiliated Hospital of Chifeng University, The Second Hospital of Hebei Medical University, The Affiliated Hospital of Inner Mongolia Medical University, Taihe Hospital，Hubei University of Medicine, The First Clinical Hospital affiliated to Harbin Medical University, Tianjin Central Hospital of Gynecology Obstetrics, Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing Maternal and Child Health Care Hospital, The Fourth Hospital Of Harbin Medical University, People's Hospital of Xinjiang Uygur Autonomous Region, Qingdao Women and Children’s Hospital, Benxi Central Hospital, Dezhou maternal and Child Health Hospital, Inner Mongolia Maternity and Child Health Care Hospital, The Second People’s Hospital and Gynecology and Obstetrics Hospital Of Fuxin city, Union Hospital Affiliated to Tongji Medical College of Huazhong University of science and technology, Liaoning Provincial Hospital for women and children, Huludao Center Hospital, The third Affiliated Hospital of Zhengzhou University, Henan Provincal Maternal and Child Health Care Hospital. Data Availability The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions. References Madar H, Goffinet F, Seco A, et al. Severe Acute Maternal Morbidity in Twin Compared With Singleton Pregnancies. Obstet Gynecol. 2019;133:1141–50. Owen MD, Cassidy AL, Weeks AD. Why are women still dying from obstetric hemorrhage? A narrative review of perspectives from high and low resource settings. Int J Obstet Anesth. 2021;46:102982. Means RT. Iron Deficiency and Iron Deficiency Anemia: Implications and Impact in Pregnancy, Fetal Development, and Early Childhood Parameters. Nutrients. 2020;12:447. Sun M, Gu T, Wu T, et al. Variation Patterns of Hemoglobin Levels by Gestational Age during Pregnancy: A Cross-Sectional Analysis of a Multi-Center Retrospective Cohort Study in China. Nutrients. 2023;15:1383. Osol G, Ko NL, Mandalà M. Plasticity of the Maternal Vasculature During Pregnancy. Annu Rev Physiol. 2019;81:89–111. Roselló-Soberón ME, Fuentes-Chaparro L, Casanueva E. Twin pregnancies: eating for three? Maternal nutrition update. Nutr Rev. 2005;63:295–02. Zulfiqar H, Shah IU, Sheas MN, et al. Dietary association of iron deficiency anemia and related pregnancy outcomes. Food Sci Nutr. 2021;9:4127–33. Ru Y, Pressman EK, Cooper EM, et al. Iron deficiency and anemia are prevalent in women with multiple gestations. Am J Clin Nutr. 2016;104:1052–60. Omotayo MO, Abioye AI, Kuyebi M, Eke AC. Prenatal anemia and postpartum hemorrhage risk: A systematic review and meta-analysis. J Obstet Gynaecol Res. 2021;47:2565–76. WHO. Haemoglobin concentrations for the diagnosis of anaemia and assessment of severity. Vitamin and Mineral Nutrition Information System. Geneva, World Health Organization, 2011 ( WHO/NMH/NHD/MNM/11.1 ) (http://www.who.int/vmnis/indicators/haemoglobin. pdf, accessed [date]). Muñoz M, Stensballe J, Ducloy-Bouthors AS, et al. Patient blood management in obstetrics: prevention and treatment of postpartum haemorrhage. A NATA consensus statement. Blood Transfus. 2019;17:112–36. Milman N. Postpartum anemia I: definition, prevalence, causes, and consequences. Ann Hematol. 2011;90:1247–53. Pavord S, Daru J, Prasannan N, et al. UK guidelines on the management of iron deficiency in pregnancy. Br J Haematol. 2020;188:819–30. Krafft A, Breymann C, Streich J, et al. Hemoglobin concentration in multiple versus singleton pregnancies–retrospective evidence for physiology not pathology. Eur J Obstet Gynecol Reprod Biol. 2001;99:184–87. Zeng Y, Li L, Mao M, et al. Establishment of reference intervals of complete blood count for twin pregnancy. BMC Pregnancy Childbirth. 2021;21:714. Anemia in Pregnancy. ACOG Practice Bulletin 233. American College of Obstetricians and Gynecologists. Obstet Gynecol. 2021;138:e55–64. Pavord S, Myers B, Robinson S, et al. UK guidelines on the management of iron deficiency in pregnancy. Br J Haematol. 2012;156:588–00. Professional Committee on Twin Pregnancy, Chinese Association of Maternal and Child Health Care. Diagnosis, treatment and healthcare guidelines for iron-deficiency anemia in twin pregnancy (2023 edition). Chin J Practical Gynecol Obstet. 2023;39:419–30. Shinar S, Shapira U, Maslovitz S. Redefining normal hemoglobin and anemia in singleton and twin pregnancies. Int J Gynaecol Obstet. 2018;142:42–7. Blickstein I, Goldschmit R, Lurie S. Hemoglobin levels during twin vs. singleton pregnancies. Parity makes the difference. J Reprod Med. 1995;40:47–50. Campbell DM, MacGillivray I. The importance of plasma volume expansion and nutrition in twin pregnancy. Acta Genet Med Gemellol (Roma). 1984;33:19–24. Al Kadri HM, Al Anazi BK, Tamim HM. Visual estimation versus gravimetric measurement of postpartum blood loss: a prospective cohort study. Arch Gynecol Obstet. 2011;283:1207–13. Rath WH. Postpartum hemorrhage–update on problems of definitions and diagnosis. Acta Obstet Gynecol Scand. 2011;90:421–28. Pranal M, Guttmann A, Ouchchane L, et al. Do estimates of blood loss differ between student midwives and midwives? A multicenter cross-sectional study. Midwifery. 2018;59:17–22. Anger H, Durocher J, Dabash R, et al. How well do postpartum blood loss and common definitions of postpartum hemorrhage correlate with postpartum anemia and fall in hemoglobin. PLoS ONE. 2019;14:e0221216. Wei Q, Xu Y, Zhang L. Towards a universal definition of postpartum hemorrhage: retrospective analysis of Chinese women after vaginal delivery or cesarean section: A case-control study. Med (Baltim). 2020;99:e21714. Quezada-Robles A, Quispe-Sarmiento F, Bendezu-Quispe G, et al. Fetal Macrosomia and Postpartum Hemorrhage in Latin American and Caribbean Region: Systematic Review and Meta-analysis. Rev Bras Ginecol Obstet. 2023;45:e706–23. Allary J, Soubirou JF, Michel J, et al. An individual scoring system for the prediction of postpartum anaemia. Ann Fr Anesth Reanim. 2013;32:e1–7. Rao A, Sairam S, Shehata H. Obstetric complications of twin pregnancies. Best Pract Res Clin Obstet Gynaecol. 2004;18:557–76. Rissanen AS, Jernman RM, Gissler M, et al. Maternal complications in twin pregnancies in Finland during 1987–2014: a retrospective study. BMC Pregnancy Childbirth. 2019;19:337. Prasad S, Beg S, Badran D, et al. Neurodevelopmental outcome in complicated twin pregnancy: prospective observational study. Ultrasound Obstet Gynecol. 2024;63:189–97. Toussia-Cohen S, Mohr-Sasson A, Tsur A, et al. Pregnancy and neonatal outcomes of twin pregnancies - the role of maternal age. J Perinat Med. 2021;49:559–65. Additional Declarations No competing interests reported. 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11:31:52","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4913305/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4913305/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":66528490,"identity":"4d7a589a-2628-4eb1-a39c-62c89971fa08","added_by":"auto","created_at":"2024-10-14 05:27:20","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":410362,"visible":true,"origin":"","legend":"\u003cp\u003eGeographical distribution of 34 hospitals across China\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-4913305/v1/6a1f546fbf76a0f61a888c8a.png"},{"id":66528493,"identity":"103222b8-f1a2-426e-a726-490c2c2fec87","added_by":"auto","created_at":"2024-10-14 05:27:21","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":80279,"visible":true,"origin":"","legend":"\u003cp\u003eFlow diagram of reference subjects in the retrospective study\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-4913305/v1/81a101e86a080fed52f04aaa.png"},{"id":66528492,"identity":"3a89ac7b-7352-472a-98dd-454ce74ccbcc","added_by":"auto","created_at":"2024-10-14 05:27:21","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":149040,"visible":true,"origin":"","legend":"\u003cp\u003eTrend chart of red blood cell (RBC), hemoglobin (Hb), and hematocrit (Hct) at different stages of pregnancy\u003c/p\u003e","description":"","filename":"Figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-4913305/v1/c99040fa597ebf50ba2f3792.png"},{"id":81907067,"identity":"5c3f41c1-f779-491b-97ef-18db6660ce86","added_by":"auto","created_at":"2025-05-04 12:46:26","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1683567,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4913305/v1/90fea306-bd18-4d48-9576-4c5b8fde9c56.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Characterization of erythrocyte parameters during twin pregnancy and risk associated with postpartum hemorrhage: a multicenter retrospective study","fulltext":[{"header":"Key Message","content":"\u003cp\u003eLow hemoglobin status in twin pregnancy is associated with the risk of postpartum hemorrhage\u003c/p\u003e\n\u003cp\u003e\u003cbr\u003e\u003c/p\u003e"},{"header":"Background","content":"\u003cp\u003eTwin pregnancy is a high-risk pregnancy state often associated with multiple complications, of which postpartum hemorrhage (PPH) is one of the most serious. Studies have shown that the incidence of PPH is significantly higher in twin pregnancies than in singleton pregnancies \u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/sup\u003e. PPH not only poses a threat to the life and health of the mother but may also cause a decline in quality of life in the long term. Therefore, early identification of pregnant women with high-risk twin pregnancies and appropriate interventions is crucial \u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eChanges in the hematologic system during pregnancy are a unique physiological state where plasma volume increases disproportionately to red blood cell (RBC) mass, resulting in the possibility of \"physiologic anemia of pregnancy\" \u003csup\u003e[\u003cspan additionalcitationids=\"CR4\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e. This change is more drastic in high-volume twin pregnancies \u003csup\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e, and therefore anemia is more common in twin pregnancies \u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e. Anemia is strongly associated with the occurrence of PPH \u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e. Hemoglobin (Hb) is an important indicator for assessing maternal anemia status, and in twin pregnancies, low Hb status may be more prevalent, and their impact on the risk of PPH has not been adequately studied. It has been suggested that there may be a correlation between low Hb status and the occurrence of PPH, but the exact cutoff value has not been defined. Therefore, it is important to determine the cut-off value of low Hb status in twin pregnancies to identify the risk associated with PPH.\u003c/p\u003e \u003cp\u003eThe aim of this study was to explore the peculiarities of twin pregnancies by comparing the changes in RBC, Hb, and hematocrit (Hct) at various stages of gestation. To explore the cut-off values of low Hb status in twin pregnancies and to assess their validity in identifying the risk of PPH. Through this study, we hope to inform clinical practice for better management of twin pregnancies and reduce the incidence of PPH.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy Population and Design:\u003c/h2\u003e \u003cp\u003e Cases for this retrospective study were obtained from 34 large Chinese hospitals, including Shengjing Hospital of China Medical University. These hospitals were located in seven geographic regions that are traditionally divided into administrative regions in China, covering most of the country (Supplementary material Fig.\u0026nbsp;1). The different colors in Fig.\u0026nbsp;1 represent the seven regions of China, and the participating hospitals are mainly divided between the eastern and central regions. Between January and December 2020, a total of 6716 cases were enrolled in this study, of which 5152 were twin cases and 1564 were singleton cases. This study was approved by the Hospital Review Committee of Shengjing Hospital (Ethics Number: 2021PS444K). The ethics committee approved the consent procedure.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eSupplementary material Fig.\u0026nbsp;1. Geographical distribution of 34 hospitals across China\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eData collection:\u003c/h2\u003e \u003cp\u003eA questionnaire was designed to collect demographic and medical information by interviewing all cases that underwent labor inspection and delivery during the study period. Medical data were extracted from each patient's medical record, including age, gravidity, parity, blood counts at various stages of pregnancy, gestational age at birth, newborn weight, pregnancy complications and co-morbidities (mainly the incidence of hypertensive disorders of pregnancy, thrombocytopenia in pregnancy, etc.), and bleeding during and after delivery.\u003c/p\u003e \u003cp\u003eAll form fillers at each hospital were trained before the survey was conducted. Each completed questionnaire was verified by a liaison officer. All the compiled data were input independently by two people and then verified by a third person.\u003c/p\u003e \u003cp\u003eAll cases in the study were eligible for inclusion in the current analysis if they had one or more of the routine blood markers for the first, second, and third trimesters, as well as medical history and pregnancy outcome data. Cases were excluded from this study for one or more of the following reasons: abnormal outcomes, such as miscarriage, intrauterine fetal death, twin pregnancies after single intrauterine fetal demise, and triplet pregnancies. Cases with missing key data (e.g., gestational age at birth, gravidity, parity, postpartum blood counts, and bleeding during labor) were also excluded.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eDefinitions and exclusion criteria:\u003c/h2\u003e \u003cp\u003eAnemia in pregnancy: according to the diagnostic criteria of WHO guidelines for anemia in pregnancy \u003csup\u003e[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e, Hb levels below 110 g/L during pregnancy were diagnosed as anemia in pregnancy. PPH: blood loss exceeding 500 mL within 24 hours after childbirth is defined as PPH \u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e. Postpartum anemia is an anemic condition characterized by Hb below 100 g/L within 24\u0026ndash;48 hours after childbirth \u003csup\u003e[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/sup\u003e. In this study, the risk associated with PPH was defined as the occurrence of either PPH or postpartum anemia following childbirth.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis:\u003c/h2\u003e \u003cp\u003eThe SPSS 26.0 statistical package was used for statistical analysis. Differences between the two groups of singleton and twin pregnancies were compared using the chi-square test or the rank-sum test. In order to observe trends in the prevalence of anemia and the levels of RBC, Hb, and Hct at each stage of pregnancy, descriptive analysis was performed using the mean and standard deviation. Differences between the groups with and without PPH risk in twin pregnancy cases were compared using the chi-square test. A logistic regression model was used to test the relationship between erythrocyte parameters and the risk associated with PPH at different stages of twin pregnancy. The feasibility of Hb predicting the risk of PPH was determined using the area under the receiver operating characteristic (ROC) curve, while the Youden index was used to determine the optimal cut-off value of Hb in predicting the risk of PPH at different stages of twin pregnancies. Sensitivity, specificity, positive predictive value, and negative predictive value were used to assess the validity of hemoglobin at different stages of twin pregnancy in the prediction of the risk of PPH.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eCharacteristics of the participating population\u003c/h2\u003e \u003cp\u003eA total of 6716 pregnant women were included in our study. The clinical records of these pregnant women were screened to exclude 261 cases with missing outcome data; 498 cases with conditions affecting blood components and hemorrhagic disorders during pregnancy were excluded. Finally, 5957 gestational cases were statistically analyzed, of which 4569 were twin pregnancies and 1388 were singleton pregnancies (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe results showed that a significantly higher proportion of women in the twin group were under 25 years old compared to the singleton group, while the proportion of older (\u0026ge;\u0026thinsp;35 years) women was relatively lower (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The proportion of women under 25 years old was 4.6% in the twin group compared with 3.1% in the singleton group; the proportion of older women was 16.8% in the twin group compared with 25.7% in the singleton group (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). In terms of preterm birth, the prevalence of preterm birth was significantly higher in the twin group than in the singleton group, 64.7% versus 6.7%, respectively (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Most of the preterm deliveries in the twin group were concentrated in the 34\u0026ndash;37 week period of gestation (47.8%). Regarding newborn weight, the proportion of low birth weight (\u0026lt;\u0026thinsp;2500 g) was also significantly higher in the twin group than in the singleton group, 55.5% versus 5.2%, respectively (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Regarding gravidity and parity, there was no significant difference between the singleton group and the twin group (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCharacteristics of the participating population\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eCharacteristics\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAll Participants, n (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eTwin pregnancies, n (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSingleton pregnancies, n (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ep-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003en\u0026thinsp;=\u0026thinsp;5957\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003en\u0026thinsp;=\u0026thinsp;4569 (76.7)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003en\u0026thinsp;=\u0026thinsp;1388 (23.3)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge at enrollment (years)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026lt;25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e251(4.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e208(4.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e43(3.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e25-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1853(31.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1460(32.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e393(28.3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e30-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2731(45.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2136(46.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e595(42.9)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e35-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e948(15.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e652(14.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e296(21.3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e174(2.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e113(2.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e61(4.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGravidity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2987(50.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2266(49.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e721(51.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.125\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2970(49.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2303(50.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e667(48.1)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePrimipara\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e4194(70.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3242(71.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e952(68.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.09\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMultipara\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1763(29.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1327(29.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e436(31.4)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGestational age at birth (weeks)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e28~\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e363 (6.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e346(7.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e17(1.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e32~\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e439 (7.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e425(9.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e14(1.0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e34~\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2249 (37.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2186(47.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e63(4.5)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2906 (48.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1612(35.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1294(93.2)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNewborn weight (g)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;1500\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e283 (4.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e277(6.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e6(0.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1500~\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e625 (10.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e603(13.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e22(1.6)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2000~\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1699 (28.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1655(36.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e44(3.2)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;2500\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3350 (56.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2034(44.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1316(94.8)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cem\u003eComparison of changes in erythrocyte parameters at various stages of pregnancy in twin versus singleton pregnancies\u003c/em\u003e \u003c/p\u003e \u003cp\u003eIn the present study, a comparison was made between the twin group and the singleton group in terms of the prevalence of anemia, stratified according to the time periods of early, middle, and late pregnancy. The results showed that the prevalence of anemia was significantly higher (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 for all) in the twin group compared to the singleton group in the first, second, and third trimesters, as shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of the prevalence of anemia at various stages of pregnancy in twin versus singleton pregnancies\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAll Participants, n (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eTwin pregnancies, n (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eSingleton pregnancies, n (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ep-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eThe first trimester\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNo.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2900\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1673\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1227\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAnemia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e184 (6.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e144 (8.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e40 (3.3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNo anemia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2716 (93.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1529 (91.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1187 (96.7)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eThe second trimester\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNo.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3622\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2457\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1165\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAnemia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1062 (29.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e872 (35.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e190 (16.3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNo anemia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2560 (70.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1585 (64.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e975 (83.7)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eThe third trimester\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNo.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4680\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3556\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1124\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAnemia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1178 (25.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1039 (22.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e139 (12.4)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNo anemia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3502 (74.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2517 (70.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e985 (87.6)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eIn the time-series comparison, RBC, Hb, and Hct showed a tendency to decrease initially and then increase slightly during the course of pregnancy, with the lowest levels in the third trimester (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Statistical analysis by the rank-sum test revealed statistical differences between the singleton group and the twin group at all three stages of pregnancy (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The mean levels of RBC, Hb, and Hct were lower in the twin group than in the singleton group. These results indicate that the changes in the erythrocyte parameters during twin pregnancies are significantly different from those during singleton pregnancies and have their own special characteristics.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of erythrocyte parameters at various stages of pregnancy in twin versus singleton pregnancies\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"16\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c13\" colnum=\"13\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c14\" colnum=\"14\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c15\" colnum=\"15\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c16\" colnum=\"16\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"5\" nameend=\"c6\" namest=\"c2\"\u003e \u003cp\u003eThe first trimester (Mean SD)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"5\" nameend=\"c11\" namest=\"c7\"\u003e \u003cp\u003eThe second trimester (Mean SD)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"5\" nameend=\"c16\" namest=\"c12\"\u003e \u003cp\u003eThe third trimester (Mean SD)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eTwin pregnancies\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eSingleton pregnancies\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003ep-value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c8\" namest=\"c7\"\u003e \u003cp\u003eTwin pregnancies\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c10\" namest=\"c9\"\u003e \u003cp\u003eSingleton pregnancies\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003ep-value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c13\" namest=\"c12\"\u003e \u003cp\u003eTwin pregnancies\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c15\" namest=\"c14\"\u003e \u003cp\u003eSingleton pregnancies\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c16\"\u003e \u003cp\u003ep-value\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003en\u0026thinsp;=\u0026thinsp;1673\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003en\u0026thinsp;=\u0026thinsp;1227\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c8\" namest=\"c7\"\u003e \u003cp\u003en\u0026thinsp;=\u0026thinsp;2457\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c10\" namest=\"c9\"\u003e \u003cp\u003en\u0026thinsp;=\u0026thinsp;1165\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c13\" namest=\"c12\"\u003e \u003cp\u003en\u0026thinsp;=\u0026thinsp;3556\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c15\" namest=\"c14\"\u003e \u003cp\u003en\u0026thinsp;=\u0026thinsp;1124\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c16\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRed blood cell (RBC)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026lt;0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3.68\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e3.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e1.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026lt;0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e3.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e0.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\"\u003e \u003cp\u003e3.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c15\"\u003e \u003cp\u003e0.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c16\"\u003e \u003cp\u003e\u0026lt;0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHemoglobin (Hb)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e125.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12.43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e129.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026lt;0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e113.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e12.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e118.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e9.46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026lt;0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e116.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e13.38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\"\u003e \u003cp\u003e120.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c15\"\u003e \u003cp\u003e9.71\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c16\"\u003e \u003cp\u003e\u0026lt;0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHematocrit (Hct)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e37.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e38.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026lt;0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e33.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e3.38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e35.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e2.95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026lt;0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e35.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e3.69\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\"\u003e \u003cp\u003e35.92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c15\"\u003e \u003cp\u003e2.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c16\"\u003e \u003cp\u003e\u0026lt;0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cem\u003eChanges in the erythrocyte parameters during twin pregnancy in relation to the risk associated with PPH\u003c/em\u003e \u003c/p\u003e \u003cp\u003eIn this study, we further analyzed a population of 4569 twin pregnancies and showed that the prevalence of those at risk associated with PPH was 44.9% (2052). Through a chi-square test, we found that there was a significant difference between the group at risk of PPH and the group without risk in parity and newborn weight (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Specifically, the group at risk of PPH demonstrated a higher proportion of primiparous deliveries and a significantly higher mean newborn weight than the group without risk. No significant differences were found between the two groups when comparing age, gravidity, and gestational age at birth (Table\u0026nbsp;\u003cspan refid=\"Tab8\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of characteristics among twin pregnancies with and without the risk of postpartum hemorrhage (PPH) In this study, we conducted a logistic analysis of the risk associated with PPH in twin pregnancies, and univariate analysis revealed that RBC, Hb, and Hct at all stages of pregnancy were significantly correlated with the risk associated with PPH (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The risk associated with PPH decreased significantly with an increase in Hb during pregnancy. Changes in RBC and Hct likewise showed an inverse correlation with the risk of postpartum hemorrhage (Table\u0026nbsp;\u003cspan refid=\"Tab9\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRisks associated with postpartum hemorrhage\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNo risk\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ep-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;4569\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;2052\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;2517\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge at enrollment (Years)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.168\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026lt;25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e208(4.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e96(4.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e112(4.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e25-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1460(32.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e625(30.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e835(33.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e30-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2136(46.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e967(47.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1169(46.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e35-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e652(14.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e316(15.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e336(13.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e113(2.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e48(2.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e65(2.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGravidity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.707\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2266(49.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1024(49.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1242(49.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2303(50.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1028(50.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1275(50.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.015\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePrimipara\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3242(71.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1493(72.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1749(69.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMultipara\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1327(29.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e559(27.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e768(30.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGestational age at birth (weeks)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.105\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e28~\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e346(7.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e135(6.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e211(8.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e32~\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e425(9.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e192(9.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e233(9.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e34~\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2186(47.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1007(49.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1179(46.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1612(35.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e718(35.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e894(35.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNewborn weight (g)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.000\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;1500\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e277(6.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e104(5.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e173(6.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1500~\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e603(13.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e231 (11.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e372 (14.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2000~\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1655(36.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e699 (34.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e956 (38.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;2500\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2034(44.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1018(49.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1016(40.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of characteristics among twin pregnancies with and without the risk of postpartum hemorrhage (PPH)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRisks associated with postpartum hemorrhage\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNo risk\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ep-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;4569\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;2052\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;2517\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge at enrollment (Years)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.168\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026lt;25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e208(4.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e96(4.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e112(4.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e25-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1460(32.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e625(30.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e835(33.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e30-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2136(46.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e967(47.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1169(46.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e35-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e652(14.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e316(15.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e336(13.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e113(2.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e48(2.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e65(2.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGravidity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.707\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2266(49.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1024(49.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1242(49.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2303(50.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1028(50.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1275(50.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.015\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePrimipara\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3242(71.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1493(72.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1749(69.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMultipara\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1327(29.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e559(27.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e768(30.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGestational age at birth (weeks)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.105\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e28~\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e346(7.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e135(6.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e211(8.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e32~\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e425(9.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e192(9.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e233(9.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e34~\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2186(47.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1007(49.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1179(46.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1612(35.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e718(35.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e894(35.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNewborn weight (g)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.000\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;1500\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e277(6.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e104(5.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e173(6.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1500~\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e603(13.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e231 (11.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e372 (14.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2000~\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1655(36.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e699 (34.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e956 (38.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;2500\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2034(44.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1018(49.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1016(40.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab6\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eLogistics regression analysis of risk associated with postpartum hemorrhage (PPH) Hb is commonly used in clinical practice as a criterion for the diagnosis of anemia; therefore, we compared data on Hb at various stages of pregnancy in twin pregnancies with the occurrence of risk associated with PPH. We assessed the sensitivity and specificity of different Hb cut-offs by plotting ROC curves to find the optimal cut-off value (Table\u0026nbsp;\u003cspan refid=\"Tab10\" class=\"InternalRef\"\u003e6\u003c/span\u003e). The area under the ROC curve (AUC) was 0.56 and 0.58 in the first and second trimesters, respectively, suggesting limited accuracy in predicting the risk of PPH in these two stages. In the third trimester, the AUC was 0.67, suggesting that Hb in the third trimester has a better value in predicting the risk of PPH. Although there were differences in the predictive ability of Hb by stage, the cut-off of Hb in the third trimester showed relatively high sensitivity and specificity. Hb was also found to be associated with the risk associated with PPH in a multifactorial analysis (Table\u0026nbsp;\u003cspan refid=\"Tab9\" class=\"InternalRef\"\u003e5\u003c/span\u003e), suggesting that Hb in the third trimester is an independent risk factor for the risk associated with PPH. More attention should be paid to monitoring Hb in the third trimester in twin pregnancies.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"11\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"5\" nameend=\"c6\" namest=\"c2\"\u003e \u003cp\u003eUnivariate analysis\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"5\" nameend=\"c11\" namest=\"c7\"\u003e \u003cp\u003eMultivariate analysis\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eExp(B)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e95%CI for Exp(B)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eExp(B)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c11\" namest=\"c10\"\u003e \u003cp\u003e95%CI for Exp(B)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThe first trimester\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRed blood cell (RBC)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.378\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.685\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.552\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.851\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-0.591\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.030\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.554\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e0.325\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e0.944\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHemoglobin (Hb)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.980\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.972\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.987\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-0.006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.599\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.994\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e0.973\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e1.016\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHematocrit (Hct)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.059\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.943\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.918\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.968\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.017\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.628\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e1.017\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e0.949\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e1.091\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThe second trimester\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRed blood cell (RBC)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.289\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.749\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.617\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.909\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.077\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.816\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e1.080\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e0.564\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e2.068\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHemoglobin (Hb)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.024\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.977\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.970\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.983\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.019\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.199\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e1.019\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e0.990\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e1.050\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHematocrit (Hct)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.078\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.925\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.903\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.948\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-0.024\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.663\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.977\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e0.878\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e1.086\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThe third trimester\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRed blood cell (RBC)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.653\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.521\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.441\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.615\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.942\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2.566\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e1.430\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e4.606\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHemoglobin (Hb)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.048\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.953\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.948\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.958\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-0.062\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.940\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e0.919\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e0.961\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHematocrit (Hct)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.156\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.855\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.838\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.873\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.017\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.680\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e1.017\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e0.939\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e1.101\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab7\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eHemoglobin (Hb) cut-off levels in different stages of twin pregnancies Finally, the level below which a low Hb status was identified was based on a cut-off value that we determined. We further categorized the twin samples with consecutive gestational data into four groups: Group A: no low Hb status throughout the pregnancy; Group B: low Hb status in 1 trimester; Group C: low Hb status in 2 trimesters; and Group D: low Hb status throughout the pregnancy. As shown in Table\u0026nbsp;\u003cspan refid=\"Tab7\" class=\"InternalRef\"\u003e7\u003c/span\u003e, as the duration of low Hb status in twin pregnancies increased, the odds ratio (OR) of risk associated with PPH was significantly higher. A similar trend was observed with regard to the risk of postpartum anemia, and the degree of risk of postpartum anemia was higher as the duration increased. In terms of the amount of labor hemorrhage, there was a statistically significant difference in group D, indicating that twin patients who had a low Hb status throughout the pregnancy had a higher risk in terms of the amount of PPH.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCut-off\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSensitivity\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSpecificity\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eThe area under the ROC curve (AUC)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e95% CI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThe first trimester\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e117.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e30.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e81.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.53\u0026ndash;0.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThe second trimester\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e108.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e39.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e73.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.56\u0026ndash;0.60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThe third trimester\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e116.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e63.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e61.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.67\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.65\u0026ndash;0.69\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab8\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 7\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe prevalence of adverse postpartum outcomes based on the duration of low hemoglobin (Hb) status\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"17\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c13\" colnum=\"13\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c14\" colnum=\"14\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c15\" colnum=\"15\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c16\" colnum=\"16\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c17\" colnum=\"17\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eN(%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eThe risk associated with postpartum hemorrhage (PPH)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eOR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003e95%CI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eThe amount of labor hemorrhage\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eOR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c12\" namest=\"c11\"\u003e \u003cp\u003e95%CI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c13\"\u003e \u003cp\u003ePostpartum anemia\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c14\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c15\"\u003e \u003cp\u003eOR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c17\" namest=\"c16\"\u003e \u003cp\u003e95%CI\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eN(%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eN(%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c12\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c13\"\u003e \u003cp\u003eN(%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c15\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c16\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGroup A\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e529(39.6%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e220(41.6%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e188(35.5%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e \u003cp\u003e71(13.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c15\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c16\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGroup B\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e386(28.9%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e188(48.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.033\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.334\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.024\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e1.737\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e139(36.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.883\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e1.021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e0.776\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e \u003cp\u003e1.342\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e \u003cp\u003e103(26.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c14\"\u003e \u003cp\u003e0.000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c15\"\u003e \u003cp\u003e2.348\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c16\"\u003e \u003cp\u003e1.677\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c17\"\u003e \u003cp\u003e3.288\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGroup C\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e280(21.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e157(56.1%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.793\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.338\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e2.402\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e98(35.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.879\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e0.977\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e0.721\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e \u003cp\u003e1.323\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e \u003cp\u003e106(37.9%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c14\"\u003e \u003cp\u003e0.000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c15\"\u003e \u003cp\u003e3.930\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c16\"\u003e \u003cp\u003e2.776\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c17\"\u003e \u003cp\u003e5.563\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGroup D\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e141(10.6%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e106(75.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4.254\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.797\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e6.470\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e66(46.8%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.015\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e1.596\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e1.096\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e \u003cp\u003e2.324\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e \u003cp\u003e87(61.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c14\"\u003e \u003cp\u003e0.000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c15\"\u003e \u003cp\u003e10.393\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c16\"\u003e \u003cp\u003e6.817\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c17\"\u003e \u003cp\u003e15.843\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe present study found that the changes in the erythrocyte parameters during twin pregnancies are more specialized than in singleton pregnancies. Because of this difference, the management of twin pregnancies should also be different from that of singleton pregnancies. Therefore, the concept of low Hb status is proposed in this study. In twin pregnancies, low Hb status in the third trimester is highly associated with the PPH. Women with twin pregnancies who remain in low Hb status for a prolonged period of time should be more vigilant for PPH and postpartum anemia.\u003c/p\u003e \u003cp\u003eBy comparing the singleton and twin groups, this study found that the prevalence of anemia in the twin group was significantly higher than that in the singleton group in the first, second, and third trimesters, which is consistent with the findings of previous studies. Twin pregnancies result in a significant increase in maternal demand for iron and other nutrients due to the increase in the number of fetuses, leading to an increase in the incidence of anemia \u003csup\u003e[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eIn addition, the present study similarly found that the levels of RBC, Hb, and Hct showed a decreasing and then slightly increasing trend with increasing gestational weeks, with the lowest level in the second trimester in both singleton and twin groups. The phenomenon is consistent with previously reported studies \u003csup\u003e[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e in the overall population of pregnancy and may be related to the imbalance between the increase in plasma volume and the increase in erythrocyte volume in the second trimester, leading to hemodilution \u003csup\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e. Therefore, the diagnostic segmental definition of anemia according to gestational stage is more in line with the changes in the erythrocyte parameters in twin pregnancies. This is consistent with the criteria for the diagnosis of anemia in pregnancy proposed by the American College of Obstetricians and Gynecologists (ACOG) and the British Committee for Standards in Haematology (BCSH). The diagnostic criteria for anemia in pregnancy is consistent \u003csup\u003e[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e. Similarly, the Chinese Twin Anemia Group has endorsed this viewpoint and suggested that stage-based diagnosis is more in line with the physiological characteristics of twin pregnancy \u003csup\u003e[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eCompared to singleton group, twin group had significantly lower RBC, Hb, and Hct at all stages. This result is consistent with other studies on hematologic system changes in twin pregnancies\u003csup\u003e[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/sup\u003e. It further supports the theory of maternal hematologic system changes during twin pregnancies\u003csup\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e.The study by Blickstein I et al. also found that the RBC and Hb in twin pregnancies were generally lower than those in singleton pregnancies, a phenomenon that may be related to the increased physiological load associated with twin pregnancies\u003csup\u003e[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/sup\u003e. The increase in blood volume is more pronounced in women with twin pregnancies, leading to more pronounced hemodilution\u003csup\u003e[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eIn this study, in order to provide an in-depth analysis of the twin pregnancy population, postpartum anemia was added to the outcome variables along with PPH as the final outcome. The assessment of postpartum blood loss in clinical work is relatively subjective and lacks precision, with many studies proposing that clinical underestimation of postpartum blood loss is common\u003csup\u003e[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/sup\u003e, and others suggesting that overestimation of a small amount of hemorrhage and underestimation of a large amount of hemorrhage occur in clinical work\u003csup\u003e[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]\u003c/sup\u003e. Postpartum anemia likewise reflects bleeding during delivery\u003csup\u003e[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e, and in a study by Anger et al.\u003csup\u003e[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/sup\u003e, it was found that the occurrence of postpartum anemia was common in women with \u0026ge;\u0026thinsp;1000 ml of blood loss during delivery. Therefore, to improve the accuracy of assessment, the present study added postpartum anemia to PPH as the criterion for determining prognosis.\u003c/p\u003e \u003cp\u003eSubsequently, this study compared those at risk of PPH with those not at risk and found significant differences in parity and newborn weight. Specifically, the group at risk for PPH showed a higher proportion of primiparous women, which is consistent with the findings of previous studies that primiparous women may be at higher risk for complications\u003csup\u003e[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/sup\u003e. The mean weight of the newborns was significantly higher in the group at risk of PPH than in the group without risk. This result may be related to the physiological characteristics of twin pregnancies, which are usually accompanied by higher fetal weights (Wang et al., 2021), which predispose to poor contractile function after uterine overstretching, and larger placental area resulting in greater hemorrhagic area, among others\u003csup\u003e[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eAlthough univariate analysis suggested that changes in the erythrocyte parameters in the first and second trimester were associated with the risk of PPH, a ROC curve was performed that revealed limitations in prediction of the risk associated with PPH at these two stages. In contrast, Hb in the third trimester was a better predictor. Moreover, multifactorial analysis found that Hb in the third trimester was associated with the risk of PPH, indicating that low Hb status in the third trimester was an independent risk factor. This finding is consistent with the findings of Allary et al.\u003csup\u003e[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]\u003c/sup\u003e, who also stated that anemia in late pregnancy is an independent risk factor for PPH. In addition, a review by Omotayo et al.\u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e also mentioned that prenatal anemia increases the risk of PPH. All these findings suggest the importance of monitoring Hb in the third trimester to reduce the risk of PPH. Unlike previous studies, this study emphasizes the important role of Hb in a population with twin pregnancies.\u003c/p\u003e \u003cp\u003eThe novelty of this study is that we proposed the concept of \"low Hb status\" for the twin pregnancy population. In twin pregnancies, due to the different physiological and pathological manifestations from singleton pregnancies\u003csup\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e, even if they are not anemic, higher hemoglobin levels are required to avoid PPH or anemia due to the demands of delivery. The cut-off values in this study are slightly higher than the WHO anemia criteria, which is for the general population, and in the case of twin pregnancies, both blood loss during labor and energy expenditure are higher than in singleton pregnancies. A slightly higher cut-off value would help to minimize complications in twin pregnancies, the cut-off value in this study aligns more closely with real-life needs.\u003c/p\u003e \u003cp\u003eFinally, we analyzed the duration of the low Hb status. We found a significant correlation between the duration of the low Hb status and peripartum quantitative blood loss, postpartum anemia, and PPH-related risk. The risk associated with PPH and the risk of postpartum anemia increased significantly with the duration of the low Hb status. With regard to the peripartum quantitative blood loss, the twin pregnancies with the low Hb status throughout the pregnancy had a higher risk of blood loss. Therefore, it is necessary to emphasize and pay attention to the specific blood changes in the twin pregnancy and refine the diagnostic criteria. We believe that this study provides more evidence for the guidance of pregnancy care in the twin pregnancy.\u003c/p\u003e \u003cp\u003eThis study examined PPH and postpartum anemia as primary outcomes, but the prognostic outcomes of twin pregnancies are multifactorial, including maternal complications\u003csup\u003e[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]\u003c/sup\u003e, the presence of complicated twins\u003csup\u003e[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]\u003c/sup\u003e, and neonatal birth status\u003csup\u003e[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]\u003c/sup\u003e, among other factors. Therefore, the cut-off value for low Hb status used in this study cannot be used as a diagnostic criterion for anemia in twin pregnancies. The relatively low impact of low Hb status on PPH in the first and second trimesters found in this study may be due to the time gap from delivery, which limits the predictive power of cut-off values in these two stages for the risk associated with PPH. Future studies need to further refine the assessment of the relevant aspects to provide stronger evidence for clinical practice in twin pregnancies.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe changes in the erythrocyte system during twin pregnancies are more specific, and the cut-off value of \"low Hb status\" proposed in this paper can help to identify the risks associated with PPH in twin mothers.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e\u003c/div\u003e"},{"header":"Declarations","content":"Ethics statement\n\nThis retrospective study was ethically approved by the Research Ethics Committee of Shengjing Hospital affiliated to China Medical University (no. 2021PS444K, Shenyang, China). Approval Date: March 10, 2021.Written informed consent was obtained from individual or guardian participants. All methods were performed in accordance with the relevant guidelines and regulations (Declaration of Helsinki).\u003cp\u003e \u003cstrong\u003eConsent for publication\u003c/strong\u003e \u003cp\u003eNot applicable\u003c/p\u003e \u003c/p\u003e\u003cp\u003e \u003ch2\u003eCompeting interests\u003c/h2\u003e \u003cp\u003eThe authors declare that they have no competing interests\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eThis study was funded by National Key Research and Development Program of China (2023YFC2705900). This study was also funded by Science and Technology Projects of Liaoning Province, China(2021JH2/10300081).\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eJYL analyzed the data, and was a major contributor in writing the manuscript. FX, J L,XY, WQY, XC, HLH, JYH, YZ and CXL participated in collecting data. SWY and JW participated in the revision and quality control of the article. JYL, YZ and CXL participated in the design of the article. All authors have read and approved the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003e The authors thank all participants in 2020 retrospective study of Twin pregnancy anemia group in China Association of Maternal and Child Health Care Professional Committee of twin pregnancy for their dedication and contributions.They thanked Jiajin Hu of China Medical University for his technical support. The hospitals participating in the 2020 retrospective study of the twin anemia group are as follows: Women's Hospital School of Medicine Zhejiang University, The First Affiliated Hospital Of Anhui Medical University, Fujian Provincial Maternity and Children's Hospital, Hunan Provincal Maternal and Child Health Care Hospital, Maternal and Child Health Hospital of Hubei Province, Tongji Medical Colleg, Huazhong University of Science and Technology, Northwest Women\u0026rsquo;s and Children\u0026rsquo;s Hospital, Nanjing Drum Tower Hospital, Gansu Provincial Maternity and Child-care Hospital, The International Peace Maternity and Child Health Hospital of The China Welfare Institute, Dalian women and children's Medical Hospital, Kunming City Maternal and Child Health Hospital, Anhui Province Maternity and Child Health Hospital, The First Affiliated Hospital of Zhengzhou University, The First Bethune Hospital of Jilin University, Affiliated Hospital of Chifeng University, The Second Hospital of Hebei Medical University, The Affiliated Hospital of Inner Mongolia Medical University, Taihe Hospital，Hubei University of Medicine, The First Clinical Hospital affiliated to Harbin Medical University, Tianjin Central Hospital of Gynecology Obstetrics, Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing Maternal and Child Health Care Hospital, The Fourth Hospital Of Harbin Medical University, People's Hospital of Xinjiang Uygur Autonomous Region, Qingdao Women and Children\u0026rsquo;s Hospital, Benxi Central Hospital, Dezhou maternal and Child Health Hospital, Inner Mongolia Maternity and Child Health Care Hospital, The Second People\u0026rsquo;s Hospital and Gynecology and Obstetrics Hospital Of Fuxin city, Union Hospital Affiliated to Tongji Medical College of Huazhong University of science and technology, Liaoning Provincial Hospital for women and children, Huludao Center Hospital, The third Affiliated Hospital of Zhengzhou University, Henan Provincal Maternal and Child Health Care Hospital.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eMadar H, Goffinet F, Seco A, et al. Severe Acute Maternal Morbidity in Twin Compared With Singleton Pregnancies. Obstet Gynecol. 2019;133:1141\u0026ndash;50.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOwen MD, Cassidy AL, Weeks AD. Why are women still dying from obstetric hemorrhage? A narrative review of perspectives from high and low resource settings. Int J Obstet Anesth. 2021;46:102982.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMeans RT. Iron Deficiency and Iron Deficiency Anemia: Implications and Impact in Pregnancy, Fetal Development, and Early Childhood Parameters. Nutrients. 2020;12:447.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSun M, Gu T, Wu T, et al. 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Br J Haematol. 2012;156:588\u0026ndash;00.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eProfessional Committee on Twin Pregnancy, Chinese Association of Maternal and Child Health Care. Diagnosis, treatment and healthcare guidelines for iron-deficiency anemia in twin pregnancy (2023 edition). Chin J Practical Gynecol Obstet. 2023;39:419\u0026ndash;30.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShinar S, Shapira U, Maslovitz S. Redefining normal hemoglobin and anemia in singleton and twin pregnancies. Int J Gynaecol Obstet. 2018;142:42\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBlickstein I, Goldschmit R, Lurie S. Hemoglobin levels during twin vs. singleton pregnancies. Parity makes the difference. J Reprod Med. 1995;40:47\u0026ndash;50.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCampbell DM, MacGillivray I. The importance of plasma volume expansion and nutrition in twin pregnancy. Acta Genet Med Gemellol (Roma). 1984;33:19\u0026ndash;24.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAl Kadri HM, Al Anazi BK, Tamim HM. Visual estimation versus gravimetric measurement of postpartum blood loss: a prospective cohort study. Arch Gynecol Obstet. 2011;283:1207\u0026ndash;13.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRath WH. Postpartum hemorrhage\u0026ndash;update on problems of definitions and diagnosis. Acta Obstet Gynecol Scand. 2011;90:421\u0026ndash;28.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePranal M, Guttmann A, Ouchchane L, et al. Do estimates of blood loss differ between student midwives and midwives? A multicenter cross-sectional study. Midwifery. 2018;59:17\u0026ndash;22.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAnger H, Durocher J, Dabash R, et al. How well do postpartum blood loss and common definitions of postpartum hemorrhage correlate with postpartum anemia and fall in hemoglobin. PLoS ONE. 2019;14:e0221216.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWei Q, Xu Y, Zhang L. Towards a universal definition of postpartum hemorrhage: retrospective analysis of Chinese women after vaginal delivery or cesarean section: A case-control study. Med (Baltim). 2020;99:e21714.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eQuezada-Robles A, Quispe-Sarmiento F, Bendezu-Quispe G, et al. Fetal Macrosomia and Postpartum Hemorrhage in Latin American and Caribbean Region: Systematic Review and Meta-analysis. Rev Bras Ginecol Obstet. 2023;45:e706\u0026ndash;23.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAllary J, Soubirou JF, Michel J, et al. An individual scoring system for the prediction of postpartum anaemia. Ann Fr Anesth Reanim. 2013;32:e1\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRao A, Sairam S, Shehata H. Obstetric complications of twin pregnancies. Best Pract Res Clin Obstet Gynaecol. 2004;18:557\u0026ndash;76.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRissanen AS, Jernman RM, Gissler M, et al. Maternal complications in twin pregnancies in Finland during 1987\u0026ndash;2014: a retrospective study. BMC Pregnancy Childbirth. 2019;19:337.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePrasad S, Beg S, Badran D, et al. Neurodevelopmental outcome in complicated twin pregnancy: prospective observational study. Ultrasound Obstet Gynecol. 2024;63:189\u0026ndash;97.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eToussia-Cohen S, Mohr-Sasson A, Tsur A, et al. Pregnancy and neonatal outcomes of twin pregnancies - the role of maternal age. J Perinat Med. 2021;49:559\u0026ndash;65.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"twin pregnancy, red blood cell parameters, low hemoglobin state, postpartum hemorrhage, postpartum anemia","lastPublishedDoi":"10.21203/rs.3.rs-4913305/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4913305/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eIntroduction:\u003c/h2\u003e \u003cp\u003eThe twin pregnancy population is a high-risk group. Twin pregnancies are at higher risk of anemia due to increased fetal demand for maternal nutrients and oxygen. In addition, changes in erythrocyte parameters during pregnancy may be specific to twin pregnancy, and these changes may be closely associated with the risk of postpartum hemorrhage (PPH). Therefore, the aim of this study was to explore the specificity of twin pregnancies by comparing the changes in red blood cell (RBC), hemoglobin concentration (Hb), and hematocrit (Hct) at various stages of gestation and to further investigate the relationship between hemoglobin levels and the risk associated with PPH in twin pregnancies.\u003c/p\u003e\u003ch2\u003eMaterial and methods:\u003c/h2\u003e \u003cp\u003eOur study was a multicenter retrospective study involving 4569 twin pregnant women, conducted in 34 hospitals nationwide in China in 2020. First, the levels of RBC, Hb, and Hct were descriptively analyzed to compare whether there were any differences between singleton and twin pregnancies. Second, in twin cases, differences were compared between those at risk for PPH and those not at risk. The subject operating characteristic (ROC) curves and area under the curve (AUC) were calculated for Hb at each stage, and the Hb cutoff value that caused the risk associated with PPH was determined using the risk associated with PPH as the criterion. Finally, the relationship between the duration of low Hb status in twin pregnancies and the risk associated with PPH was explored.\u003c/p\u003e\u003ch2\u003eResults:\u003c/h2\u003e \u003cp\u003e(1) RBC, Hb, and Hct were low at all stages of twin pregnancies compared with singleton pregnancies. (2) In twin pregnancy, \"low Hb status\" at all stages of pregnancy was associated with the risk of PPH. We believe that Hb below 116.5 g/L in the third trimester should be considered a warning against the risk of PPH. (3) The duration of \"low hemoglobin status\" in twin pregnancy is associated with the risk of PPH.\u003c/p\u003e\u003ch2\u003eConclusions:\u003c/h2\u003e \u003cp\u003eThis study shows that the changes in erythrocyte parameters during twin pregnancies are more specific, and the proposed cut-off value of \"low Hb status\" in twin pregnancy may help to identify the risk of PPH.\u003c/p\u003e","manuscriptTitle":"Characterization of erythrocyte parameters during twin pregnancy and risk associated with postpartum hemorrhage: a multicenter retrospective study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-10-14 05:27:15","doi":"10.21203/rs.3.rs-4913305/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"7415580e-7cb1-4687-b35d-78784ff37f2a","owner":[],"postedDate":"October 14th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-05-04T12:38:17+00:00","versionOfRecord":[],"versionCreatedAt":"2024-10-14 05:27:15","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4913305","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4913305","identity":"rs-4913305","version":["v1"]},"buildId":"cTy_lsJlmDsVRNrSptgXS","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}