Pregnancy Complications and Risk of Uterine Rupture Among Women With Singleton Pregnancies in China

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Methods: We obtained all data from China’s National Maternal Near Miss Surveillance System (NMNMSS) between 2012 and 2018. Poisson regression analysis was used to assess the risk of UR with pregnancy complications (preeclampsia, gestational diabetes mellitus, placental abruption, placenta previa and placenta percreta) among 9,454,239 pregnant women. Furthermore, we analysed the risks of UR with pregnancy complications in different gestational age groups. Results: Compared with women without pregnancy complications, those with different complications (except for preeclampsia) had a 1- to 3-fold greater risk of UR. These associations also persisted in women without a previous caesarean delivery. Moreover, an increased risk of UR before term birth was observed among women with gestational diabetes mellitus, placental abruption and placenta percreta. A large for gestational age (LGA) foetus increased the risk of UR in women with gestational diabetes mellitus, especially at 32 to 36 weeks gestation. Conclusions: Better quality antenatal care and early intervention for women with these pregnancy complications are needed to minimize the incidence of UR. Maternal & Fetal Medicine Pregnancy complications Uterine rupture Risk factors Large for gestational age Preterm delivery Figures Figure 1 Figure 2 Background Uterine rupture (UR) is a tear in the uterine wall that occurs before or during labour. It poses considerable risks for adverse maternal and perinatal outcomes, including serious health risks for both mother (e.g., maternal death) and foetus (e.g., stillbirth, neonatal death)[ 1 , 2 ]. Mounting evidence supports that a history of caesarean section is a major risk factor for UR in subsequent pregnancies[ 1 , 3 ], and the risk increases with the number of previous cesarean deliveries[ 4 , 5 ]. The incidence of UR varies across countries, ranging from 0.18 to 9 cases per 1,000 pregnant women[ 1 , 6 , 7 ]. Many countries have created policies to decrease caesarean rates[ 8 , 9 ], but the UR rate has increased over the years[ 10 , 11 ]. It is unknown whether the increasing rate of UR is due to the effects of potential risk factors related to a history of caesarean section. Evidence suggests that women who have a history of caesarean section may be at increased risk of pregnancy complications, such as placental abruption, placenta previa, placenta percreta, gestational diabetes mellitus and preeclampsia[ 12 – 14 ]. These pregnancy complications may be partly considered manifestations of dysfunctional placental function[ 15 , 16 ]. To date, placenta percreta has been reported to be associated with an increased risk of UR[ 17 , 18 ]. However, there are limited data on the association of other pregnancy complications with UR. A few studies with small sample sizes have analysed the impacts of diabetes and hypertension on the risk of UR[ 7 , 19 , 20 ], but these studies have yielded different conclusions. In addition, current guidelines only discuss the impact of vaginal trial delivery after caesarean section on the occurrence of UR [ 21 , 22 ], but the effects of pregnancy complications related to previous caesarean deliveries have not been reported. If a link between pregnancy complications and UR is confirmed, it may provide additional preventive measures. We hypothesize that pregnancy complications (preeclampsia, gestational diabetes mellitus, placental abruption, placenta previa, placenta percreta) may be associated with an increased risk of UR. Therefore, our study analysed more than 9 million singleton pregnant women from China’s National Maternal Near Miss Surveillance System (NMNMSS) to evaluate whether these pregnancy complications were associated with the risk of UR. By analysing the impact of each pregnancy complication in different gestational age groups, we provided insights into the early interventions that would contribute to reducing the incidence of UR in pregnant women. Methods Design and setting We obtained data from China’s NMNMSS between 2012 and 2018. The system covers 438 hospitals in 326 districts or counties throughout 30 provinces, each of which manages more than 1,000 deliveries annually[11]. Data collected included sociodemographic characteristics, obstetric history, pregnancy complications, and pregnancy outcomes of all pregnant or postpartum women in a hospital. Doctors in each hospital were trained to collect data prospectively from admission to discharge. Quality assurance was ensured by staff from county-level, municipal-level and provincial-level maternal and child health hospitals 1–2 times a year. At the same time, the National Office for Maternal and Child Health Surveillance verified the quality of the records by selecting 6–8 hospitals randomly in each province once a year[23]. Study population We restricted the analysis to pregnant women with singleton births who delivered at or after 28 complete weeks of gestation. Women with multiple pregnancies were not included because they are prone to pregnancy complications[24] and UR[25]. Women lacking information on delivery method, history of caesarean section, or gravidity were excluded. We also excluded women with an unlikely combination of gravidity and parity. This left a total of 9,454,239 women for the study. Variable definition UR was defined as uterine or lower uterine dehiscence during late pregnancy or delivery[26]. According to the degree of dehiscence, UR can be divided into complete UR (tearing in all layers of the uterine wall) and incomplete UR (tearing in the muscular layers)[10]. Common clinical manifestations of UR include foetal distress, sudden tearing uterine pain, cessation of uterine contractions and abnormal vaginal bleeding[27]. UR was diagnosed by a health professional with imaging techniques (magnetic resonance imaging or ultrasound examination)[28]; or during emergency caesarean delivery; or peripartum hysterectomy or laparotomy after vaginal birth[3]. Unfortunately, UR is captured as a dichotomous variable (yes/no) in the NMNMSS, and the type of rupture is lacking. We identified five pregnancy complications related to previous caesarean delivery for analysis: preeclampsia, gestational diabetes mellitus, placental abruption, placenta previa and placenta percreta[13, 14]. Preeclampsia included pregnancies with preeclampsia, eclampsia or HELLP (haemolysis, elevated liver enzymes and low platelets) syndrome, as well as chronic hypertension with superimposed preeclampsia. Gestational diabetes was diagnosed by an oral glucose tolerance test (OGTT) during pregnancy. Placental abruption was defined as the premature separation of the implanted placenta before delivery. Placenta previa was defined as the placenta covering the internal os of the cervix. Placenta percreta, as the most severe grade of the placenta accreta spectrum disorders, occurs when the chorionic villi penetrate the uterine serosa[29]. We selected variables that may be related to the occurrence of UR, including region, hospital level, education level (none, primary school, middle school, high school, college or higher), maternal age at delivery (<20, 20–24, 25–29, 30–34, 35–39 and ≥40 years), the number of antenatal visits (none, 1–3, 4–6, 7–9, ≥10), gravidity (1, 2–3, ≥4), parity (0, 1, ≥2), number of previous caesarean deliveries (0, 1, ≥2), foetal presentation (cephalic and other abnormal lies), gestational age, birthweight, and mode of delivery (vaginal delivery and caesarean section). We divided China’s regions into three categories (eastern, central and western) and classified hospitals into three levels (the first level represents the smallest hospital) according to standard definitions[23]. Gestational age was defined based on ultrasound measurement results or estimated from the date of the last menstrual period and classified as early preterm (28–33 weeks), late preterm (34–36 weeks), or term (≥ 37 weeks). Large for gestational age (LGA) was defined as a gestational age-adjusted birth weight above the 90th percentile[30]. Other factors thought to be associated with UR included gestational hypertension, chronic hypertension, heart disease, hepatic disease, severe anaemia (haemoglobin concentration lower than 70 g/L), infection (excluding abortion-related infection, puerperal infection and abdominal incision infection), thrombophlebitis, renal disease, lung disease, and connective tissue disorders. Statistical Analysis Primary analysis We expressed the UR rate as the number of pregnant women with UR per 1,000 pregnant women. Since some women giving birth in township hospitals were not included in the NMNMSS, we weighted the UR rate for the sampling distribution of the population according to the 2010 census of China, as detailed elsewhere[23]. Moreover, a history of caesarean section is a major risk factor for UR in subsequent pregnancies[1, 3], and the risk increases with the number of previous caesarean deliveries[4, 5]. Thus, we calculated the previous caesarean deliveries adjusted rate of UR in women by using the margins command in Stata[31]. We classified pregnancy complications into mutually exclusive categories: preeclampsia, gestational diabetes mellitus, placental abruption, placenta previa, and placenta percreta. We used Poisson regression with a robust variance estimator to assess the association of UR with pregnancy complications, reporting the results from two models. The reference for each model was women without any of the five pregnancy complications. Model 1 describes the adjusted relative risk (aRR) and 95% confidence Interval (CI), taking into account the sampling distribution of the population and birth clustering within hospitals, medical institutions, and pregnant women's sociodemographic and clinical factors that might contribute to the observed associations. Model 2 adjusted for the covariates in Model 1 as well as the number of previous caesarean deliveries (0, 1, ≥2) and LGA (yes/no). We did not adjust for gestational age or final mode of delivery because they included consequences of UR (i.e., laparotomy due to UR). To identify the most robust and stable model, we investigated both multicollinearity and model goodness-of-fit. Due to a history of caesarean section related to both pregnancy complications[1, 3] and UR[12–14], pregnancy complications may be only an intermediate factor in the causal chain between a history of caesarean section and the risk of UR. We repeated the association analysis of pregnancy complications with UR only in women without previous caesarean delivery. Secondary analysis Restricting to a group of women To investigate the association between pregnancy complications and UR without potential maternal confounding factors (advanced maternal age[1] and multiple gravidities[32]), we performed sensitivity analyses excluding women with advanced maternal age (≥35 years) and/or multiple gravidities (≥4). Given the possible impacts of abnormal foetal presentation and macrosomia on the occurrence of UR[33], we restricted the association analysis to women with offspring having a cephalic lie and a birth weight of less than or equal to 4000 g. Co-occurrence of pregnancy complications and UR risk Pregnancy complications may co-occur in a given pregnancy. We therefore repeated model 1 and 2 testing for the associations between having at least two or more pregnancy complications and the risk of UR. Because the numbers were too small to assess unique combinations of pregnancy complications, we modelled the variables “no pregnancy complications”, “any one pregnancy complication”, and “any two or more pregnancy complications” in a single model. Risk of UR in different gestational age groups To explore the risk of UR with pregnancy complications in different gestational age groups, we compared the UR rates in women for each pregnancy complication and gestational age against those in women without pregnancy complications at 28–33 weeks of gestational age, using model 1 and 2. Role of large for gestational age Because LGA is associated with gestational diabetes mellitus[34], we repeated model 1 and 2 testing to analyse a possible effect of LGA foetuses on the risk of UR among women with gestational diabetes mellitus. Trends over time in UR rates To examine trends over time in UR rates among women with pregnancy complications, we repeated model 1 and 2 by including the year of study period as a continuous variable. Statistical analysis was performed using Stata (version 16.0, Stata Corp LP., College Station, United States of America). P<0.05 (2-sided) was considered statistically significant. Patient involvement Informed consent from the patients was waived by the Ethics Committee, as the data used in our study were obtained from a national routine surveillance system established by the government. Data use was authorized by the National Health Commission, and data provided to us were deidentified. Results Of the 9,454,239 pregnant women enrolled in this study, 885,087 (9.4%) women had pregnancy complications. Compared with women without pregnancy complications, women with pregnancy complications tended to be older, to have multiple gravidities and to have had previous caesarean deliveries. At the time of birth, women with pregnancy complications had a higher percentage of abnormal foetal presentations and LGA. Details are summarized in Table 1 . Table 1 Maternal and fetal characteristics of 9,454,239 pregnant women with singleton births Sociodemographic characteristic Women without pregnancy complications, n (%) Women with pregnancy complications, n (%) P value n = 8,569,152 (90.6%) n = 885,087 (9.4%) Region of China East 2,407,580 (88.5) 313,912 (11.5) P < 0.001 Central 3,464,042 (91.9) 304,138 (8.1) West 2,697,530 (91.0) 267,037 (9.0) Hospital level Unknown 457,421 (95.2) 23,264 (4.8) P < 0.001 Level 1 569,527 (96.8) 18,536 (3.2) Level 2 4,094,405 (93.3) 295,839 (6.7) Level 3 3,447,799 (86.3) 547,448 (13.7) Maternal education None 42,037 (90.3) 4,523 (9.7) P < 0.001 Primary school 259,703 (91.8) 23,323 (8.2) Middle school 2,821,827 (93.9) 182,270 (6.1) High school 2,309,079 (90.8) 235,360 (9.2) College or higher 2,977,190 (87.9) 409,826 (12.1) Unknown 159,316 (84.2) 29,785 (15.8) Mother’s age, years < 20 229,174 (96.5) 8,387 (3.5) P < 0.001 20–24 1,742,770 (95.3) 86,051 (4.7) 25–29 3,554,091 (92.1) 303,454 (7.9) 30–34 1,941,052 (87.7) 272,915 (12.3) 35–39 699,991 (82.3) 150,716 (17.7) ≥ 40 153,702 (77.4) 45,001 (22.6) Unknown 248,372 (93.0) 18,563 (7.0) Antenatal care visits None 106,694 (92.0) 9,327 (8.0) P < 0.001 1–3 586,349 (93.0) 43,983 (7.0) 4–6 2,599,192 (93.9) 169,815 (6.1) 7–9 2,576,046 (90.5) 271,105 (9.5) ≥ 10 2,480,962 (87.5) 353,423 (12.5) Unknown 219,909 (85.5) 37,434 (14.5) Gravidity 1 3,440,750 (92.0) 297,971 (8.0) P < 0.001 2–3 4,092,602 (90.7) 421,269 (9.3) ≥ 4 1,035,800 (86.2) 165,847 (13.8) Parity 0 4,848,051 (91.1) 474,646 (8.9) P < 0.001 1 3,209,056 (90.0) 356,733 (10.0) ≥ 2 512,045 (90.5) 53,708 (9.5) Previous caesarean deliveries 0 7,274,553 (91.3) 692,669 (8.7) P < 0.001 1 1,220,781 (87.1) 180,214 (12.9) ≥ 2 73,818 (85.8) 12,204 (14.2) Foetal presentation Cephalic 8,298,133 (90.8) 839,684 (9.2) P < 0.001 abnormal lies 267,253 (85.8) 44,191 (14.2) Unknown 3,766 (75.7) 1,212 (24.3) Large for gestational age No 7,759,647 (91.0) 764,956 (9.0) P < 0.001 Yes 809,505 (87.1) 120,131 (12.9) Delivery method Vaginal 4,944,933 (93.9) 321,071 (6.1) P < 0.001 Caesarean section 3,624,219 (86.5) 564,016 (13.5) Overall, 8.8% of the women had a single pregnancy complication (830,648) and 0.6% had two or more (54,439). Thus, most pregnancy complications occurred as single events (Fig. 1 ). Among these, gestational diabetes mellitus was the most common pregnancy complication, followed by preeclampsia, placenta previa, placental abruption and placenta percreta. Trends over time in UR rates There were 16,949 pregnant women with UR, giving a weighted UR rate of 1.6 cases per thousand pregnant women. Figure 2 shows that the rate of UR was markedly higher in women with pregnancy complications than in women without pregnancy complications, irrespective of medical institution or the pregnant woman's sociodemographic and clinical factors. Moreover, the rate of UR in women with pregnancy complications increased as the ratio of women with pregnancy complications increased between 2012 and 2018. However, there was no change in the UR rate in women with pregnancy complications over time after adjustment for the number of previous caesarean deliveries and all other risk factors (Model 2, aRR: 1.44, 95% CI: 0.91–2.29, Additional file Table S1). Similarly, the UR rate did not change over time in women with each pregnancy complication after adjustment (Additional file Table S1). Risk of UR stratified by history of caesarean section The incidence of UR varied in women with different single-complications (Table 2 ), with the highest rate in women with placenta percreta. Except for preeclampsia, the other four pregnancy complications were associated with a significantly increased risk of UR after adjustment for risk factors (Table 2 ). After excluding women with previous caesarean deliveries, these associations were substantially elevated. Among women without previous caesarean delivery, the adjusted risk of UR was 1.41 (95% CI: 1.21–1.65) for women with gestational diabetes mellitus, 5.03 (95% CI: 3.40–7.42) for women with placental abruption, 5.38 (95% CI: 3.76–7.70) for women with placenta previa, and 12.79 (95% CI: 7.69–21.27) for women with placenta percreta (Table 2 ). Table 2 Risk of uterine rupture with pregnancy complications Pregnancy complications * No. UR UR rate # Adjusted UR rate ## aRR (95%CI): Model 1 a P value aRR (95%CI): Model 2 b P value All women None 13,651 1.4 1.4 1 (reference) 1 (reference) Preeclampsia 338 1.7 1.5 0.97 (0.76–1.24) 0.825 0.89 (0.70–1.14) 0.358 Gestational diabetes mellitus 1,812 3.2 2.5 1.36 (1.16–1.60) < 0.001 1.20 (1.03–1.41) 0.020 Placental abruption 175 5.6 5.4 2.44 (1.79–3.33) < 0.001 2.74 (2.04–3.66) < 0.001 Placenta previa 520 6.4 3.7 2.13 (1.64–2.77) < 0.001 1.72 (1.33–2.22) < 0.001 Placenta percreta 88 13.5 6.2 3.81 (2.48–5.83) < 0.001 2.64 (1.71–4.07) < 0.001 Women without previous caesarean delivery None 1,808 0.2 – 1 (reference) 1 (reference) Preeclampsia 46 0.3 – 1.02 (0.69–1.49) 0.938 1.02 (0.69–1.49) 0.933 Gestational diabetes mellitus 199 0.4 – 1.43 (1.22–1.67) < 0.001 1.41 (1.21–1.65) < 0.001 Placental abruption 46 1.9 – 4.98 (3.38–7.34) < 0.001 5.03 (3.40–7.42) < 0.001 Placenta previa 116 2.1 – 5.36 (3.76–7.66) < 0.001 5.38 (3.76–7.70) < 0.001 Placenta percreta 25 6.7 – 12.77 (7.69–21.23) < 0.001 12.79 (7.69–21.27) < 0.001 * Each one of pregnancy complications has no other complications. None: Women with none of the five pregnancy complications. # Weighted uterine rupture rate per 1000 women ## Weighted, and previous caesarean deliveries adjusted uterine rupture rate per 1000 women a Model 1: adjusted for sampling distribution of population and clustering of births within hospitals, region, hospital level, the number of antenatal visits, the women’s educational level, maternal age at delivery, parity, foetal presentation, gestational hypertension, chronic hypertension, heart disease, hepatic disease, severe anaemia, infection, thrombophlebitis, renal disease, lung disease, connective tissue disorders. b Model 2: adjusted for Model 1 as well as the number of previous caesarean deliveries (0, 1, ≥ 2) and large for gestational age (yes/no). The results were similar after restricting the dataset to those women without advanced maternal age and multiple gravidities (Additional file Table S2). When women with offspring having abnormal foetal presentation and a birth weight of more than 4000 g were excluded, the risks of UR with pregnancy complications were largely unchanged (Additional file Table S3). Co-occurrence of pregnancy complications and UR risk Compared with having none of the five pregnancy complications, having two or more complications was associated with a statistically significant almost 1.42–fold risk of UR (Model 1, aRR: 1.88, 95% CI: 1.51–2.34; Model 2, aRR: 1.42, 95% CI:1.14–1.77). Risk of UR in different gestational age groups For a small proportion (14.9%, 2,531 of 16,949) of women with UR, the rupture occurred before term birth. An increased risk of UR before term birth was observed among women with gestational diabetes mellitus, placental abruption and placenta percreta (Table 3 ). Women with placenta percreta had the highest risk of UR at 28 to 33 weeks gestation (Model 2, aRR: 6.21, 95% CI: 3.43–11.24). The risk of UR among women with gestational diabetes mellitus was only observed at 34 to 36 weeks gestation (Model 2, aRR: 1.43, 95% CI: 1.03–1.97). Moreover, the risk of UR among women with placenta previa was only observed at term (Model 2, aRR: 1.41, 95% CI: 1.08–1.86). Table 3 Association between pregnancy complications and uterine rupture by gestational age group Pregnancy complications * Gestational age group (week) Early preterm (28–33) Late preterm (34–36) Term (≥ 37) No. UR None 312 1,430 11,909 Preeclampsia 20 72 246 Gestational diabetes mellitus 41 198 1,573 Placental abruption 40 51 84 Placenta previa 46 138 336 Placenta percreta 16 11 61 UR rate # (Adjusted UR rate ## ) None 2.5 (2.5) 3.8 (3.4) 1.3 (1.3) Preeclampsia 1.0 (0.7) 2.3 (1.7) 1.7 (1.6) Gestational diabetes mellitus 4.7 (3.4) 6.4 (4.3) 3.0 (2.3) Placental abruption 6.6 (5.0) 7.5 (5.7) 4.6 (5.5) Placenta previa 5.9 (3.5) 5.9 (3.0) 6.6 (4.1) Placenta percreta 46.0 (25.1) 15.7 (6.0) 10.9 (5.1) aRR (95%CI) : Model 1 a None 1 (reference) 1.72 (1.29–2.30) c 0.72 (0.57–0.91) d Preeclampsia 0.25 (0.14–0.44) c 0.78 (0.44–1.38) 0.89 (0.61–1.31) Gestational diabetes mellitus 1.29 (0.96–1.73) 1.84 (1.32–2.57) c 1.00 (0.75–1.33) Placental abruption 1.69 (1.17–2.46) d 2.23 (1.62–3.06) c 1.85 (1.38–2.50) c Placenta previa 1.27 (0.89–1.82) 1.34 (0.89–2.03) 1.91 (1.44–2.53) c Placenta percreta 7.99 (4.43–14.40) c 3.10 (1.65–5.82) c 2.52 (1.73–3.69) c aRR (95%CI) : Model 2 b None 1 (reference) 1.47 (1.12–1.92) d 0.67 (0.53–0.85) d Preeclampsia 0.21 (0.12–0.38) c 0.63 (0.36–1.12) 0.77 (0.51–1.14) Gestational diabetes mellitus 1.13 (0.84–1.53) 1.43 (1.03–1.97) e 0.82 (0.62–1.08) Placental abruption 1.60 (1.00–2.31) e 2.13 (1.55–2.92) c 2.12 (1.60–2.81) c Placenta previa 1.08 (0.76–1.54) 0.97 (0.67–1.43) 1.41 (1.08–1.86) e Placenta percreta 6.21 (3.43–11.24) c 1.92 (0.99–3.71) 1.60 (1.08–2.38) e * Each one of pregnancy complications has no other complications. None: Women with none of the five pregnancy complications. # Weighted uterine rupture rate per 1000 women ## Weighted, and previous caesarean deliveries adjusted uterine rupture rate per 1000 women a Model 1: adjusted for sampling distribution of population and clustering of births within hospitals, region, hospital level, the number of antenatal visits, the women’s educational level, maternal age at delivery, parity, foetal presentation, gestational hypertension, chronic hypertension, heart disease, hepatic disease, severe anaemia, infection, thrombophlebitis, renal disease, lung disease, connective tissue disorders. b Model 2: adjusted for Model 1 as well as the number of previous caesarean deliveries (0, 1, ≥ 2) and large for gestational age (yes/no). c P < 0.001; d P < 0.01; e P < 0.05 Role of large for gestational age The risk of UR in women with gestational diabetes mellitus without an LGA foetus was 1.18–fold (Model 2, aRR: 1.18, 95% CI: 1.00–1.38), and the risk was slightly larger in women with gestational diabetes mellitus and an LGA foetus (Model 2, aRR: 1.28, 95% CI: 1.09–1.50) (Table 4 ). Among women at 34–36 weeks gestational age, the association between gestational diabetes mellitus with an LGA foetus and UR was slightly elevated (Model 2, aRR: 1.40, 95% CI: 1.09–1.79) (Table 4 ). Table 4 The association between gestational diabetes mellitus and uterine rupture Gestational diabetes mellitus No. UR UR rate # Adjusted UR rate ## aRR (95%CI): Model 1 a P value aRR (95%CI): model 2 b P value All women None only 12,138 1.4 1.5 1 (reference) 1 (reference) None and LGA 1,513 1.7 1.3 1.02 (0.95–1.11) 0.550 0.96 (0.89–1.04) 0.335 Gestational diabetes mellitus only 1,452 3.0 2.5 1.32 (1.11–1.56) 0.001 1.18 (1.00–1.38) 0.046 Gestational diabetes mellitus and LGA 360 4.1 2.5 1.59 (1.34–1.88) < 0.001 1.28 (1.09–1.50) 0.003 Women at 34–36 weeks gestational age None only 1,274 3.7 4.3 1 (reference) 1 (reference) None and LGA 156 4.2 3.6 1.02 (0.81–1.30) 0.841 0.92 (0.73–1.15) 0.459 Gestational diabetes mellitus only 140 5.4 4.8 1.00 (0.81–1.23) 0.968 0.92 (0.76–1.12) 0.414 Gestational diabetes mellitus and LGA 58 10.9 6.5 1.77 (1.38–2.26) < 0.001 1.40 (1.09–1.79) 0.009 * Gestational diabetes mellitus: Women with no other four complications. None: Women with none of the five pregnancy complications. LGA: Large for gestational age. # Weighted uterine rupture rate per 1000 women ## Weighted, and previous caesarean deliveries adjusted uterine rupture rate per 1000 women a Model 1: adjusted for sampling distribution of population and clustering of births within hospitals, region, hospital level, the number of antenatal visits, the women’s educational level, maternal age at delivery, parity, foetal presentation, gestational hypertension, chronic hypertension, heart disease, hepatic disease, severe anaemia, infection, thrombophlebitis, renal disease, lung disease, connective tissue disorders. b Model 2: adjusted for Model 1 as well as the number of previous caesarean deliveries (0, 1, ≥ 2). Discussion Using data from more than 9 million singleton pregnant women in China, we found that approximately one-tenth of all women had pregnancy complications, and most occurred as single events. The incidence of UR varied in women with different single-complications, and the highest rate was observed in women with placenta percreta. Gestational diabetes mellitus, placental abruption, placenta previa and placenta percreta were associated with a substantially increased risk of UR, andthe risks for UR were 1- to 3-fold higher among women with these pregnancy complications. These associations persisted in women without previous caesarean delivery. Moreover, a significantly increased risk of UR before term birth was observed in women with gestational diabetes mellitus, placental abruption and placenta percreta. An LGA foetus increased the risk of UR in women with gestational diabetes mellitus, especially at 32 to 36 weeks gestation. In our data, the largest increased risk of UR was seen for placenta percreta (aRR: 2.64, 95% CI: 1.71–4.07). Among women without previous caesarean delivery, the risk of UR was approximately 13 times higher in women with placenta percreta than in those without pregnancy complications (aRR: 12.79, 95% CI: 7.69–21.27). A large retrospective cohort study from Negev found that pregnant women with placenta accreta spectrum disorders (including placenta percreta) had a significantly increased risk of UR (OR: 6.42, 95% CI: 2.0–20.4)[ 17 ]. Moreover, previous research found that UR occurs in women without a history of caesarean section[ 3 , 35 , 36 ] and identified spontaneous UR due to placenta percreta as occurring in a primigravida woman without prior uterine operation[ 37 ]. Thus, our findings are consistent with previous studies, suggesting that placenta percreta (especially without previous caesarean delivery) may increase the risk of UR. To date, few studies have reported the impact of other pregnancy complications on the occurrence of UR and have mainly focused on the impact of preeclampsia/eclampsia and diabetes mellitus. However, there are inconsistent conclusions regarding the effects of preeclampsia/eclampsia and gestational diabetes mellitus on UR risk. A population-based Negev study of 138 pregnant women with UR found that hypertension disorders (including preeclampsia/eclampsia) were associated with a twofold increased risk of UR (OR: 2.05, 95% CI: 1.20–3.50), but diabetes mellitus (prepregnancy and gestation) was not related to the risk of UR (OR: 0.87, 95% CI: 0.41–1.86)[ 7 ]. However, this study was limited because the diagnoses of hypertension disorder and diabetes mellitus did not distinguish between different subtypes. In contrast, we found that gestational diabetes mellitus increased the risk of UR (aRR: 1.20, 95% CI: 1.03–1.41), but preeclampsia did not increase the risk of UR (aRR: 0.89, 95% CI: 0.70–1.14). Our finding is similar to results from two previous studies, where gestational diabetes increased the risk of UR (aOR: 5.78, 95% CI: 1.12–20.00)[ 19 ], and eclampsia was not related to the risk of UR (aOR: 0.08, 95% CI: 0.01–0.71)[ 20 ]. Furthermore, we found that approximately six percent of women had two or more pregnancy complications. A previous study identified placenta previa as often occurring alongside placenta accreta, leading to a higher incidence of bleeding complications[ 38 ]. Moreover, placental abruption concurrently presents with preeclampsia in the same pregnancy, and these two complications have a similar pathogenesis, such as placental ischaemia[ 15 ]. The cooccurrence of preeclampsia and placental abruption was associated with worse maternal, foetal and neonatal outcomes (e.g., stillbirth/neonatal deaths)[ 39 ]. However, the combined effect of pregnancy complications on the risk of UR has been less closely studied. Our results indicate that having two or more pregnancy complications may increase the risk of UR (Model 2, aRR: 1.42, 95% CI: 1.14–1.77), but we failed to assess the effects of unique combinations due to small samples. The pathophysiological mechanism underlying the relationship between pregnancy complications and the occurrence of UR remains unclear. The occurrence of UR may be directly or indirectly caused by a weak myometrium and excessive expansion of the uterine cavity. We speculate that the increased risk of UR may be due to pregnancy complications themselves through a specific mechanism. For example, UR from placenta percreta occurs because the placental villi invade the myometrium at the site of placental implantation (particularly at a previous scar site), resulting in UR[ 18 ]. In our study, we found that placenta percreta was still associated with an increased risk of UR in women without previous caesarean delivery. The possible reason for this might be the thinning of the uterus after multiple induced abortions, resulting in placental percreta leading to UR. In addition, we hypothesize that pregnancy complications may indirectly increase the occurrence of UR by increasing the occurrence of certain obstetric complications. Our results support the hypothesis that gestational diabetes mellitus in combination with LGA may increase the risk of UR. In our study, we found that the association between gestational diabetes mellitus without an LGA foetus and UR was 1.18–fold (Model 2, aRR: 1.18, 95% CI: 1.00–1.38), and the risk of UR was slightly larger in women with gestational diabetes mellitus and an LGA foetus (especially at 34–36 weeks gestational age). Our findings raise the possibility that UR may occur during late pregnancy among diabetic women, when excess foetal growth leads to excessive expansion of the uterine cavity. Future research is required to investigate the mechanism of pregnancy complications on the occurrence of UR. UR often occurs before or during labour without warning. The risk of UR can increase in the presence of predisposing factors, such as a history of caesarean section and its related pregnancy complications. Clinicians may tend to focus on women with a history of caesarean delivery, ignoring those without such a history but with complications during pregnancy. Current guidelines developed by the American College of Obstetricians and Gynaecologists (ACOG) and Royal College of Obstetricians and Gynaecologists (RCOG) place a strong emphasis on the impact of vaginal trial delivery after caesarean section on UR[ 21 , 22 ]. Unfortunately, there is currently a lack of guidelines for pregnant women with pregnancy complications to prevent the occurrence of UR. For example, current guidelines developed by the ACOG only recommend that women with gestational diabetes mellitus should be counselled regarding the risks and benefits of a scheduled caesarean delivery when the estimated foetal weight is 4,500 g or more[ 40 ]. In our study, we found that an LGA foetus (especially at 34–36 weeks gestational age) was associated with an increased risk of UR in women with gestational diabetes mellitus. Our findings suggest that controlling weight throughout pregnancy for women with gestational diabetes mellitus may play an important role in preventing the occurrence of UR. Additionally, we found that UR occurred only at term for women with placenta previa. Our findings support the recommendation that women with uncomplicated placenta previa should have a planned delivery at 36–-37 weeks of gestation to avoid haemorrhage[ 41 ]. Moreover, evidence has shown that an accurate prenatal diagnosis and a standardized multidisciplinary team approach improve the pregnancy outcomes of women with placenta percreta[ 42 ]. Thus, standardized protocols for prenatal diagnosis and management of pregnancy complications should be established throughout pregnancy to reduce the occurrence of UR. Our study has a number of strengths. First, we used common protocols to collect data through uniformly trained clinicians, so the data quality was high. Second, the large sample size allowed us to analyse the risk of UR with pregnancy complications in several subgroups. Third, we were able to adjust for several potential confounders (e.g., the number of previous caesarean deliveries, LGA, abnormal foetal presentation, advanced maternal age, multiple gravidities, coexisting comorbidity, etc. ). We acknowledge some limitations within this study. First, there may be a possibility of the underreporting of pregnancy complications in our retrospective study. Additionally, some women with pregnancy complications may lost to follow up, when they abandoned treatment or were transferred to other non-monitoring hospitals. However, some women with pregnancy complications may also be transferred from other non-monitoring hospitals into monitoring hospitals in the NMNMSS. Second, we were unable to obtain several variables that may have been related to the occurrence of UR, including information on the intended mode of delivery[ 43 ], the interval between this pregnancy and the last caesarean section[ 33 ], and the history of other uterine operations (e.g., myomectomy)[ 44 ]. Third, there was a lack of information on the duration and severity of pregnancy complications in our study, and there may be deviations in evaluating the impact of pregnancy complications on the risk of UR. Fourth, we did not distinguish between complete and partial UR[ 10 ], so we could not analyse the influence of pregnancy complications on the different types of UR. Therefore, the estimation of UR risk may be biased. Conclusions Our study identified that gestational diabetes mellitus, placental abruption, placenta previa and placenta percreta increased the risk of UR. An increased risk of UR before term birth was observed among women with gestational diabetes mellitus, placental abruption and placenta percreta. Furthermore, an LGA foetus increased the risk of UR in women with gestational diabetes mellitus, especially at 32 to 36 weeks gestation. Thus, physicians should provide early, better antenatal care and intervention for women with these high-risk pregnancy complications. Abbreviations NMNMSS: National Maternal Near Miss Surveillance System; UR: uterine rupture; LGA: large for gestational age; HELLP:haemolysis, elevated liver enzymes and low platelets; OGTT: oral glucose tolerance test; aRR: adjusted relative risk; CI: confidence Interval; ACOG: American College of Obstetricians and Gynaecologists; RCOG: Royal College of Obstetricians and Gynaecologists Declarations Acknowledgements We thank the institutions and staff of the National Maternal Near Miss Surveillance System Authors’ contributions JT, JL and JZ conceived the study. YM and YX X managed the dataset and PR C conducted the analyses. JT wrote the first draft of the manuscript. All authors provided intellectual input and contributed and approved the final manuscript. Funding This study has received funding by The National Key Research and Development Program of China (2018YFC1002200), The Sichuan province Key Research and Development Program of China (No. 2019YFS0530). Availability of data and materials The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request. Ethics approval and consent to participate This study was approved by the Ethics Review Committee of West China Second University Hospital, Sichuan University(Protocol ID: 2012008; date of approval: 3 March 2012), and conducted in accordance with the principles of the Declaration of Helsinki. Because of the retrospective design of this study, the Ethics Review Committee of West China Second University Hospital, Sichuan University has waived the requirement of the informed consent for this study. Consent for publication All authors have read and approved the content, and agree to submit it for consideration for publication in your journal. Competing Interests The authors declare no competing interests. References Kaczmarczyk M, Sparén P, Terry P, Cnattingius S. Risk factors for uterine rupture and neonatal consequences of uterine rupture: a population-based study of successive pregnancies in Sweden. BJOG: An International Journal of Obstetrics & Gynaecology. 2007;114:1208–14. Motomura K, Ganchimeg T, Nagata C, Ota E, Vogel JP, Betran AP, et al. Incidence and outcomes of uterine rupture among women with prior caesarean section: WHO Multicountry Survey on Maternal and Newborn Health. Sci Rep. 2017;7:44093. Zwart J, Richters J, Öry F, de Vries J, Bloemenkamp K, van Roosmalen J. Uterine rupture in the Netherlands: a nationwide population-based cohort study: Uterine rupture in the Netherlands. BJOG: An International Journal of Obstetrics & Gynaecology. 2009;116:1069–80. Tahseen S, Griffiths M. Vaginal birth after two caesarean sections (VBAC-2)-a systematic review with meta-analysis of success rate and adverse outcomes of VBAC-2 versus VBAC-1 and repeat (third) caesarean sections. BJOG. 2010;117:5–19. Caughey AB, Shipp TD, Repke JT, Zelop CM, Cohen A, Lieberman E. Rate of uterine rupture during a trial of labor in women with one or two prior cesarean deliveries. Am J Obstet Gynecol. 1999;181:872–6. Al-Zirqi I, Stray-Pedersen B, Forsén L, Vangen S. Uterine rupture after previous caesarean section: Uterine rupture. BJOG: An International Journal of Obstetrics & Gynaecology. 2010;117:809–20. Ronel D, Wiznitzer A, Sergienko R, Zlotnik A, Sheiner E. Trends, risk factors and pregnancy outcome in women with uterine rupture. Arch Gynecol Obstet. 2012;285:317–21. Caughey AB, Cahill AG, Guise J-M, Rouse DJ. Safe prevention of the primary cesarean delivery. American Journal of Obstetrics and Gynecology. 2014;210:179–93. Xia X, Zhou Z, Shen S, Lu J, Zhang L, Huang P, et al. Effect of a two-stage intervention package on the cesarean section rate in Guangzhou, China: A before-and-after study. PLoS Med. 2019;16:e1002846. Al-Zirqi I, Stray-Pedersen B, Forsén L, Daltveit A-K, Vangen S. Uterine rupture: trends over 40 years. BJOG: Int J Obstet Gy. 2016;123:780–7. Liang J, Mu Y, Li X, Tang W, Wang Y, Liu Z, et al. Relaxation of the one child policy and trends in caesarean section rates and birth outcomes in China between 2012 and 2016: observational study of nearly seven million health facility births. BMJ. 2018;:k817. Getahun D, Oyelese Y, Salihu HM, Ananth CV. Previous Cesarean Delivery and Risks of Placenta Previa and Placental Abruption. Obstet Gynecol. 2006;107:771–8. Daltveit AK, Tolla MC, Irgens LM. Cesarean Delivery and Subsequent Pregnancies. Obstet Gynecol. 2008;111:1327–34. Hu H-T, Xu J-J, Lin J, Li C, Wu Y-T, Sheng J-Z, et al. Association between first caesarean delivery and adverse outcomes in subsequent pregnancy: a retrospective cohort study. BMC Pregnancy Childbirth. 2018;18:273. Ananth CV. Ischemic placental disease: A unifying concept for preeclampsia, intrauterine growth restriction, and placental abruption. Semin Perinatol. 2014;38:131–2. Brosens I, Pijnenborg R, Vercruysse L, Romero R. The “Great Obstetrical Syndromes” are associated with disorders of deep placentation. American Journal of Obstetrics and Gynecology. 2011;204:193–201. Eshkoli T, Weintraub AY, Sergienko R, Sheiner E. Placenta accreta: risk factors, perinatal outcomes, and consequences for subsequent births. American Journal of Obstetrics and Gynecology. 2013;208:219.e1-219.e7. Gupta N, Gupta A, Green M, Kang HS, Blankstein J. Placenta Percreta at 17 Weeks with Consecutive Hysterectomy: A Case Report and Review of the Literature. Case Reports in Obstetrics and Gynecology. 2012;2012:1–4. Getahun WT, Solomon AA, Kassie FY, Kasaye HK, Denekew HT. Uterine rupture among mothers admitted for obstetrics care and associated factors in referral hospitals of Amhara regional state, institution-based cross-sectional study, Northern Ethiopia, 2013–2017. PLoS ONE. 2018;13:e0208470. Vilchez G, Nazeer S, Kumar K, Warren M, Dai J, Sokol R. Contemporary epidemiology and novel predictors of uterine rupture: a nationwide population–based study. Arch Gynecol Obstet. 2017;296:869–75. Royal College of Obstetricians and Gynaecogists., A, B, C, D, E, et al. Birth after Previous Caesarean Birth (Green-Top Guideline No. 45). 2015. American College of Obstetricians and Gynaecologists., A, B, C, D, E, et al. ACOG Practice Bulletin No. 205: Vaginal Birth After Cesarean Delivery. Obstet Gynecol. 2019;133:e110–27. Zhu J, Liang J, Mu Y, Li X, Guo S, Scherpbier R, et al. Sociodemographic and obstetric characteristics of stillbirths in China: a census of nearly 4 million health facility births between 2012 and 2014. The Lancet Global Health. 2016;4:e109–18. McIntyre HD, Catalano P, Zhang C, Desoye G, Mathiesen ER, Damm P. Gestational diabetes mellitus. Nat Rev Dis Primers. 2019;5:47. Tarney CM, Whitecar P, Sewell M, Grubish L, Hope E. Rupture of an Unscarred Uterus in a Quadruplet Pregnancy. Obstet Gynecol. 2013;121:483–5. Liang J, Mu Y, Li X, Tang W, Wang Y, Liu Z, et al. Relaxation of the one child policy and trends in caesarean section rates and birth outcomes in China between 2012 and 2016: observational study of nearly seven million health facility births. BMJ. 2018;360:k817. Toppenberg KS, Block WA. Uterine rupture: what family physicians need to know. Am Fam Physician. 2002;66:823–8. Murphy DJ. Uterine rupture. Curr Opin Obstet Gynecol. 2006;18:135–40. Jauniaux E, Collins S, Burton GJ. Placenta accreta spectrum: pathophysiology and evidence-based anatomy for prenatal ultrasound imaging. Am J Obstet Gynecol. 2018;218:75–87. Zhu L, Zhang R, Zhang S, Shi W, Yan W, Wang X, et al. Chinese neonatal birth weight curve for different gestational age. Zhonghua Er Ke Za Zhi. 2015;53:97–103. Williams R. Using the Margins Command to Estimate and Interpret Adjusted Predictions and Marginal Effects. The Stata Journal. 2012;12:308–31. Abebe F, Mannekulih E, Megerso A, Idris A, Legese T. Determinants of uterine rupture among cases of Adama city public and private hospitals, Oromia, Ethiopia: a case control study. Reprod Health. 2018;15:161. Al-Zirqi I, Daltveit AK, Forsén L, Stray-Pedersen B, Vangen S. Risk factors for complete uterine rupture. American Journal of Obstetrics and Gynecology. 2017;216:165.e1-165.e8. Fadl HE, Östlund IKM, Magnuson AFK, Hanson USB. Maternal and neonatal outcomes and time trends of gestational diabetes mellitus in Sweden from 1991 to 2003. Diabetic Medicine. 2010;27:436–41. Thisted DLA, Mortensen LH, Krebs L. Uterine rupture without previous caesarean delivery: a population-based cohort study. European Journal of Obstetrics & Gynecology and Reproductive Biology. 2015;195:151–5. Fitzpatrick KE, Kurinczuk JJ, Alfirevic Z, Spark P, Brocklehurst P, Knight M. Uterine Rupture by Intended Mode of Delivery in the UK: A National Case-Control Study. PLoS Med. 2012;9:e1001184. Kinoshita T, Ogawa K, Yasumizu T, Kato J. Spontaneous rupture of the uterus due to placenta percreta at 25-weeks’ gestation: a case report. J Obstet Gynaecol Res. 1996;22:125–8. Usta IM, Hobeika EM, Abu Musa AA, Gabriel GE, Nassar AH. Placenta previa-accreta: Risk factors and complications. American Journal of Obstetrics and Gynecology. 2005;193:1045–9. Han M, Liu D, Zeb S, Li C, Tong M, Li X, et al. Are maternal and neonatal outcomes different in placental abruption between women with and without preeclampsia? Placenta. 2019;85:69–73. American College of Obstetricians and Gynaecologists., A, B, C, D, E, et al. ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus. Obstet Gynecol. 2018;131:e49–64. Spong CY, Mercer BM, D’Alton M, Kilpatrick S, Blackwell S, Saade G. Timing of Indicated Late-Preterm and Early-Term Birth. Obstetrics & Gynecology. 2011;118:323–33. Shamshirsaz AA, Fox KA, Salmanian B, Diaz-Arrastia CR, Lee W, Baker BW, et al. Maternal morbidity in patients with morbidly adherent placenta treated with and without a standardized multidisciplinary approach. American Journal of Obstetrics and Gynecology. 2015;212:218.e1-218.e9. Vandenberghe G, Bloemenkamp K, Berlage S, Colmorn L, Deneux-Tharaux C, Gissler M, et al. The International Network of Obstetric Survey Systems study of uterine rupture: a descriptive multi-country population-based study. BJOG: Int J Obstet Gy. 2019;126:370–81. Getahun WT, Solomon AA, Kassie FY, Kasaye HK, Denekew HT. Uterine rupture among mothers admitted for obstetrics care and associated factors in referral hospitals of Amhara regional state, institution-based cross-sectional study, Northern Ethiopia, 2013–2017. PLoS ONE. 2018;13:e0208470. Additional Declarations No competing interests reported. Supplementary Files Supplementaryfiles0906.docx Cite Share Download PDF Status: Published Journal Publication published 16 Feb, 2022 Read the published version in BMC Pregnancy and Childbirth → Version 2 posted Editorial decision: Major revision 24 Nov, 2021 Reviews received at journal 24 Oct, 2021 Reviewers agreed at journal 13 Oct, 2021 Reviewers agreed at journal 24 Sep, 2021 Reviewers invited by journal 21 Sep, 2021 Editor assigned by journal 21 Sep, 2021 Editor invited by journal 15 Sep, 2021 Submission checks completed at journal 15 Sep, 2021 First submitted to journal 08 Sep, 2021 You are reading this latest preprint version Show more versions Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-424294","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[{"code":1,"date":"2021-04-20 14:48:07","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}}],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":55855464,"identity":"5e126187-226f-4d9f-bad9-b7747263e4ec","order_by":0,"name":"Jing Tao","email":"","orcid":"","institution":"National Office for Maternal and Child Health Surveillance of China, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Jing","middleName":"","lastName":"Tao","suffix":""},{"id":55855465,"identity":"f1dc89c8-b582-41c3-83b8-12482534b82a","order_by":1,"name":"Yi Mu","email":"","orcid":"","institution":"National Office for Maternal and Child Health Surveillance of China, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Yi","middleName":"","lastName":"Mu","suffix":""},{"id":55855466,"identity":"e04bcfa8-ed2b-4f0f-8340-42a81d175856","order_by":2,"name":"Peiran Chen","email":"","orcid":"","institution":"National Office for Maternal and Child Health Surveillance of China, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Peiran","middleName":"","lastName":"Chen","suffix":""},{"id":55855467,"identity":"317aad5c-a000-45d2-8784-067572af5bde","order_by":3,"name":"Yanxia Xie","email":"","orcid":"","institution":"National Office for Maternal and Child Health Surveillance of China, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Yanxia","middleName":"","lastName":"Xie","suffix":""},{"id":55855468,"identity":"6791f410-66bb-4f77-b50a-abb8d0454a27","order_by":4,"name":"Juan Liang","email":"","orcid":"","institution":"National Office for Maternal and Child Health Surveillance of China, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Juan","middleName":"","lastName":"Liang","suffix":""},{"id":55855469,"identity":"32314790-29fc-431b-8196-201ea3ef59c8","order_by":5,"name":"Jun Zhu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAzElEQVRIiWNgGAWjYDACCQYGAyApx8/e2PjwAwlabIwlew43G0sQqwUI0hI33EhvE+AhRof87B6DYt4dhxlnznzYBtRvJ6fbQEAL45wzBsa8Zw4z80sntj0oYEg2NjtAQAuzRA5QS9thNsnZie0GEgwHErcR0sIG1cJjcPNgmwQPMVp4IFrSJAxuMBKpRUIircBwbpuNgWRPIjCQDYjwi/yM5G0Gb9sk6vvZjz98+KHCTo6gFpB3DBBsA9zKkAHzA+LUjYJRMApGwYgFAK30PjQPz8DsAAAAAElFTkSuQmCC","orcid":"","institution":"National Office for Maternal and Child Health Surveillance of China, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Jun","middleName":"","lastName":"Zhu","suffix":""}],"badges":[],"createdAt":"2021-04-15 05:14:05","currentVersionCode":2,"declarations":"","doi":"10.21203/rs.3.rs-424294/v2","doiUrl":"https://doi.org/10.21203/rs.3.rs-424294/v2","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12884-022-04465-w","type":"published","date":"2022-02-16T18:48:47+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":14349660,"identity":"9085fd47-b955-4e80-9337-e4ff00d6ed04","added_by":"auto","created_at":"2021-10-08 15:19:39","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":104359,"visible":true,"origin":"","legend":"Type and percent of observed pregnancy complications among 875,245 pregnant women\nNote: We did show more than 0.3% of observed combinations of pregnancy complications among 885,087 pregnant women.\nLess than 1% of observed combinations of pregnancy complications were not labelled. GD: Gestational diabetes, PE: Preeclampsia, PP: Placenta praevia, PA: Placental abruption, PPE: Placenta percreta.","description":"","filename":"Fig1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-424294/v2/fbab05514f2d58f093043eee.jpg"},{"id":14349658,"identity":"c111705d-de51-4b8a-8854-4fcdf18b2001","added_by":"auto","created_at":"2021-10-08 15:19:39","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":120792,"visible":true,"origin":"","legend":"Uterine rupture rate and the ratio of women with pregnancy complications, China, 2012-2018\nNote: The UR rate was weighted for the sampling distribution of the population covered by the Chinese National Maternal Near Miss Surveillance System.\nRatio of women with pregnancy complications was the ratio of women with pregnancy complications to all women.","description":"","filename":"Fig2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-424294/v2/f2629beb5eba88c4160fdff6.jpg"},{"id":18295087,"identity":"3d19f53a-37b1-4d5a-bb5a-26bdb228a559","added_by":"auto","created_at":"2022-02-16 18:48:50","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":855891,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-424294/v2/163cb9e8-9cd7-42e2-8b17-a0263473c4c9.pdf"},{"id":14349659,"identity":"bb81d0a6-070d-4007-b176-1e0f00d51e69","added_by":"auto","created_at":"2021-10-08 15:19:39","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":39011,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementaryfiles0906.docx","url":"https://assets-eu.researchsquare.com/files/rs-424294/v2/7c55be77fd4f84678b776bbd.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003ePregnancy Complications and Risk of Uterine Rupture Among Women With Singleton Pregnancies in China\u003c/p\u003e","fulltext":[{"header":"Background","content":"\u003cp\u003eUterine rupture (UR) is a tear in the uterine wall that occurs before or during labour. It poses considerable risks for adverse maternal and perinatal outcomes, including serious health risks for both mother (e.g., maternal death) and foetus (e.g., stillbirth, neonatal death)[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Mounting evidence supports that a history of caesarean section is a major risk factor for UR in subsequent pregnancies[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e], and the risk increases with the number of previous cesarean deliveries[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. The incidence of UR varies across countries, ranging from 0.18 to 9 cases per 1,000 pregnant women[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Many countries have created policies to decrease caesarean rates[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], but the UR rate has increased over the years[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. It is unknown whether the increasing rate of UR is due to the effects of potential risk factors related to a history of caesarean section.\u003c/p\u003e \u003cp\u003eEvidence suggests that women who have a history of caesarean section may be at increased risk of pregnancy complications, such as placental abruption, placenta previa, placenta percreta, gestational diabetes mellitus and preeclampsia[\u003cspan additionalcitationids=\"CR13\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. These pregnancy complications may be partly considered manifestations of dysfunctional placental function[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. To date, placenta percreta has been reported to be associated with an increased risk of UR[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. However, there are limited data on the association of other pregnancy complications with UR. A few studies with small sample sizes have analysed the impacts of diabetes and hypertension on the risk of UR[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], but these studies have yielded different conclusions. In addition, current guidelines only discuss the impact of vaginal trial delivery after caesarean section on the occurrence of UR [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], but the effects of pregnancy complications related to previous caesarean deliveries have not been reported. If a link between pregnancy complications and UR is confirmed, it may provide additional preventive measures.\u003c/p\u003e \u003cp\u003eWe hypothesize that pregnancy complications (preeclampsia, gestational diabetes mellitus, placental abruption, placenta previa, placenta percreta) may be associated with an increased risk of UR. Therefore, our study analysed more than 9\u0026nbsp;million singleton pregnant women from China\u0026rsquo;s National Maternal Near Miss Surveillance System (NMNMSS) to evaluate whether these pregnancy complications were associated with the risk of UR. By analysing the impact of each pregnancy complication in different gestational age groups, we provided insights into the early interventions that would contribute to reducing the incidence of UR in pregnant women.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cstrong\u003eDesign and setting\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe obtained data from China\u0026rsquo;s NMNMSS between 2012 and 2018. The system covers 438 hospitals in 326 districts or counties throughout 30 provinces, each of which manages more than 1,000 deliveries annually[11]. Data collected included sociodemographic characteristics, obstetric history, pregnancy complications, and pregnancy outcomes of all pregnant or postpartum women in a hospital. Doctors in each hospital were trained to collect data prospectively from admission to discharge. Quality assurance was ensured by staff from county-level, municipal-level and provincial-level maternal and child health hospitals 1\u0026ndash;2 times a year. At the same time, the National Office for Maternal and Child Health Surveillance verified the quality of the records by selecting 6\u0026ndash;8 hospitals randomly in each province once a year[23].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStudy population\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe restricted the analysis to pregnant women with singleton births who delivered at or after 28 complete weeks of gestation. Women with multiple pregnancies were not included because they are prone to pregnancy complications[24] and UR[25]. Women lacking information on delivery method, history of caesarean section, or gravidity were excluded. We also excluded women with an unlikely combination of gravidity and parity. This left a total of 9,454,239 women for the study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eVariable definition\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eUR was defined as uterine or lower uterine dehiscence during late pregnancy or delivery[26]. According to the degree of dehiscence, UR can be divided into complete UR (tearing in all layers of the uterine wall) and incomplete UR (tearing in the muscular layers)[10]. Common clinical manifestations of UR include foetal distress, sudden tearing uterine pain, cessation of uterine contractions and abnormal vaginal bleeding[27]. UR was diagnosed by a health professional with imaging techniques (magnetic resonance imaging or ultrasound examination)[28]; or during emergency caesarean delivery; or peripartum hysterectomy or laparotomy after vaginal birth[3]. Unfortunately, UR is captured as a dichotomous variable (yes/no) in the NMNMSS, and the type of rupture is lacking. We identified five pregnancy complications related to previous caesarean delivery for analysis: preeclampsia, gestational diabetes mellitus, placental abruption, placenta previa and placenta percreta[13, 14]. Preeclampsia included pregnancies with preeclampsia, eclampsia or HELLP (haemolysis, elevated liver enzymes and low platelets) syndrome, as well as chronic hypertension with superimposed preeclampsia. Gestational diabetes was diagnosed by an oral glucose tolerance test (OGTT) during pregnancy. Placental abruption was defined as the premature separation of the implanted placenta before delivery. Placenta previa was defined as the placenta covering the internal os of the cervix. Placenta percreta, as the most severe grade of the placenta accreta spectrum disorders, occurs when the chorionic villi penetrate the uterine serosa[29].\u003c/p\u003e\n\u003cp\u003eWe selected variables that may be related to the occurrence of UR, including region, hospital level, education level (none, primary school, middle school, high school, college or higher), maternal age at delivery (\u0026lt;20, 20\u0026ndash;24, 25\u0026ndash;29, 30\u0026ndash;34, 35\u0026ndash;39 and \u0026ge;40 years), the number of antenatal visits (none, 1\u0026ndash;3, 4\u0026ndash;6, 7\u0026ndash;9, \u0026ge;10), gravidity (1, 2\u0026ndash;3, \u0026ge;4), parity (0, 1, \u0026ge;2), number of previous caesarean deliveries (0, 1, \u0026ge;2), foetal presentation (cephalic and other abnormal lies), gestational age, birthweight, and mode of delivery (vaginal delivery and caesarean section). We divided China\u0026rsquo;s regions into three categories (eastern, central and western) and classified hospitals into three levels (the first level represents the smallest hospital) according to standard definitions[23]. Gestational age was defined based on ultrasound measurement results or estimated from the date of the last menstrual period and classified as early preterm (28\u0026ndash;33 weeks), late preterm (34\u0026ndash;36 weeks), or term (\u0026ge; 37 weeks). Large for gestational age (LGA) was defined as a gestational age-adjusted birth weight above the 90th percentile[30]. Other factors thought to be associated with UR included gestational hypertension, chronic hypertension, heart disease, hepatic disease, severe anaemia (haemoglobin concentration lower than 70 g/L), infection (excluding abortion-related infection, puerperal infection and abdominal incision infection), thrombophlebitis, renal disease, lung disease, and connective tissue disorders.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatistical Analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePrimary analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe expressed the UR rate as the number of pregnant women with UR per 1,000 pregnant women. Since some women giving birth in township hospitals were not included in the NMNMSS, we weighted the UR rate for the sampling distribution of the population according to the 2010 census of China, as detailed elsewhere[23]. Moreover, a history of caesarean section is a major risk factor for UR in subsequent pregnancies[1, 3], and the risk increases with the number of previous caesarean deliveries[4, 5]. Thus, we calculated the previous caesarean deliveries adjusted rate of UR in women by using the \u003cem\u003emargins\u003c/em\u003e command in Stata[31].\u003c/p\u003e\n\u003cp\u003eWe classified pregnancy complications into mutually exclusive categories: preeclampsia, gestational diabetes mellitus, placental abruption, placenta previa, and placenta percreta. We used Poisson regression with a robust variance estimator to assess the association of UR with pregnancy complications, reporting the results from two models. The reference for each model was women without any of the five pregnancy complications. Model 1 describes the adjusted relative risk (aRR) and 95% confidence Interval (CI), taking into account the sampling distribution of the population and birth clustering within hospitals, medical institutions, and pregnant women\u0026apos;s sociodemographic and clinical factors that might contribute to the observed associations. Model 2 adjusted for the covariates in Model 1 as well as the number of previous caesarean deliveries (0, 1, \u0026ge;2) and LGA (yes/no). We did not adjust for gestational age or final mode of delivery because they included consequences of UR (i.e., laparotomy due to UR). To identify the most robust and stable model, we investigated both multicollinearity and model goodness-of-fit.\u003c/p\u003e\n\u003cp\u003eDue to a history of caesarean section related to both pregnancy complications[1, 3] and UR[12\u0026ndash;14], pregnancy complications may be only an intermediate factor in the causal chain between a history of caesarean section and the risk of UR. We repeated the association analysis of pregnancy complications with UR only in women without previous caesarean delivery.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSecondary analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRestricting to a group of women\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo investigate the association between pregnancy complications and UR without potential maternal confounding factors (advanced maternal age[1] and multiple gravidities[32]), we performed sensitivity analyses excluding women with advanced maternal age (\u0026ge;35 years) and/or multiple gravidities (\u0026ge;4). Given the possible impacts of abnormal foetal presentation and macrosomia on the occurrence of UR[33], we restricted the association analysis to women with offspring having a cephalic lie and a birth weight of less than or equal to 4000 g.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCo-occurrence of pregnancy complications and UR risk\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ePregnancy complications may co-occur in a given pregnancy. We therefore repeated model 1 and 2 testing for the associations between having at least two or more pregnancy complications and the risk of UR. Because the numbers were too small to assess unique combinations of pregnancy complications, we modelled the variables \u0026ldquo;no pregnancy complications\u0026rdquo;, \u0026ldquo;any one pregnancy complication\u0026rdquo;, and \u0026ldquo;any two or more pregnancy complications\u0026rdquo; in a single model.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRisk of UR in different gestational age groups\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo explore the risk of UR with pregnancy complications in different gestational age groups, we compared the UR rates in women for each pregnancy complication and gestational age against those in women without pregnancy complications at 28\u0026ndash;33 weeks of gestational age, using model 1 and 2.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRole of large for gestational age\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eBecause LGA is associated with gestational diabetes mellitus[34], we repeated model 1 and 2 testing to analyse a possible effect of LGA foetuses on the risk of UR among women with gestational diabetes mellitus.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTrends over time in UR rates\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo examine trends over time in UR rates among women with pregnancy complications, we repeated model 1 and 2 by including the year of study period as a continuous variable.\u003c/p\u003e\n\u003cp\u003eStatistical analysis was performed using Stata (version 16.0, Stata Corp LP., College Station, United States of America). P\u0026lt;0.05 (2-sided) was considered statistically significant.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePatient involvement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eInformed consent from the patients was waived by the Ethics Committee, as the data used in our study were obtained from a national routine surveillance system established by the government. Data use was authorized by the National Health Commission, and data provided to us were deidentified.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eOf the 9,454,239 pregnant women enrolled in this study, 885,087 (9.4%) women had pregnancy complications. Compared with women without pregnancy complications, women with pregnancy complications tended to be older, to have multiple gravidities and to have had previous caesarean deliveries. At the time of birth, women with pregnancy complications had a higher percentage of abnormal foetal presentations and LGA. Details are summarized in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab1\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eMaternal and fetal characteristics of 9,454,239 pregnant women with singleton births\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eSociodemographic characteristic\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eWomen without pregnancy complications, n (%)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eWomen with pregnancy complications, n (%)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003en\u0026thinsp;=\u0026thinsp;8,569,152 (90.6%)\u003c/strong\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003en\u0026thinsp;=\u0026thinsp;885,087 (9.4%)\u003c/strong\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\" align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eRegion of China\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eEast\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2,407,580 (88.5)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e313,912 (11.5)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd rowspan=\"3\" align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eCentral\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3,464,042 (91.9)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e304,138 (8.1)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eWest\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2,697,530 (91.0)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e267,037 (9.0)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\" align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eHospital level\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eUnknown\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e457,421 (95.2)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e23,264 (4.8)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd rowspan=\"4\" align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eLevel 1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e569,527 (96.8)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e18,536 (3.2)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eLevel 2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4,094,405 (93.3)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e295,839 (6.7)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eLevel 3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3,447,799 (86.3)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e547,448 (13.7)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\" align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eMaternal education\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eNone\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e42,037 (90.3)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4,523 (9.7)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd rowspan=\"6\" align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePrimary school\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e259,703 (91.8)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e23,323 (8.2)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eMiddle school\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2,821,827 (93.9)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e182,270 (6.1)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eHigh school\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2,309,079 (90.8)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e235,360 (9.2)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eCollege or higher\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2,977,190 (87.9)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e409,826 (12.1)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eUnknown\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e159,316 (84.2)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e29,785 (15.8)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\" align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eMother\u0026rsquo;s age, years\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026lt;\u0026thinsp;20\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e229,174 (96.5)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e8,387 (3.5)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd rowspan=\"7\" align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e20\u0026ndash;24\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1,742,770 (95.3)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e86,051 (4.7)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e25\u0026ndash;29\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3,554,091 (92.1)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e303,454 (7.9)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e30\u0026ndash;34\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1,941,052 (87.7)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e272,915 (12.3)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e35\u0026ndash;39\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e699,991 (82.3)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e150,716 (17.7)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026ge;\u0026thinsp;40\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e153,702 (77.4)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e45,001 (22.6)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eUnknown\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e248,372 (93.0)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e18,563 (7.0)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\" align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eAntenatal care visits\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eNone\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e106,694 (92.0)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e9,327 (8.0)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd rowspan=\"6\" align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1\u0026ndash;3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e586,349 (93.0)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e43,983 (7.0)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4\u0026ndash;6\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2,599,192 (93.9)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e169,815 (6.1)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e7\u0026ndash;9\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2,576,046 (90.5)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e271,105 (9.5)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026ge;\u0026thinsp;10\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2,480,962 (87.5)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e353,423 (12.5)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eUnknown\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e219,909 (85.5)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e37,434 (14.5)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\" align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eGravidity\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3,440,750 (92.0)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e297,971 (8.0)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd rowspan=\"3\" align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2\u0026ndash;3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4,092,602 (90.7)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e421,269 (9.3)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026ge;\u0026thinsp;4\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1,035,800 (86.2)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e165,847 (13.8)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\" align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eParity\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4,848,051 (91.1)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e474,646 (8.9)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd rowspan=\"3\" align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3,209,056 (90.0)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e356,733 (10.0)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026ge;\u0026thinsp;2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e512,045 (90.5)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e53,708 (9.5)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\" align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003ePrevious caesarean deliveries\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e7,274,553 (91.3)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e692,669 (8.7)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd rowspan=\"3\" align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1,220,781 (87.1)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e180,214 (12.9)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026ge;\u0026thinsp;2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e73,818 (85.8)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e12,204 (14.2)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\" align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eFoetal presentation\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eCephalic\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e8,298,133 (90.8)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e839,684 (9.2)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd rowspan=\"3\" align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eabnormal lies\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e267,253 (85.8)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e44,191 (14.2)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eUnknown\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3,766 (75.7)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1,212 (24.3)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\" align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eLarge for gestational age\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eNo\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e7,759,647 (91.0)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e764,956 (9.0)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eYes\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e809,505 (87.1)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e120,131 (12.9)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\" align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eDelivery method\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eVaginal\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4,944,933 (93.9)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e321,071 (6.1)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eCaesarean section\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3,624,219 (86.5)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e564,016 (13.5)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eOverall, 8.8% of the women had a single pregnancy complication (830,648) and 0.6% had two or more (54,439). Thus, most pregnancy complications occurred as single events (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). Among these, gestational diabetes mellitus was the most common pregnancy complication, followed by preeclampsia, placenta previa, placental abruption and placenta percreta.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTrends over time in UR rates\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThere were 16,949 pregnant women with UR, giving a weighted UR rate of 1.6 cases per thousand pregnant women. Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e shows that the rate of UR was markedly higher in women with pregnancy complications than in women without pregnancy complications, irrespective of medical institution or the pregnant woman's sociodemographic and clinical factors. Moreover, the rate of UR in women with pregnancy complications increased as the ratio of women with pregnancy complications increased between 2012 and 2018. However, there was no change in the UR rate in women with pregnancy complications over time after adjustment for the number of previous caesarean deliveries and all other risk factors (Model 2, aRR: 1.44, 95% CI: 0.91\u0026ndash;2.29, Additional file Table S1). Similarly, the UR rate did not change over time in women with each pregnancy complication after adjustment (Additional file Table S1).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRisk of UR stratified by history of caesarean section\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe incidence of UR varied in women with different single-complications (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e), with the highest rate in women with placenta percreta. Except for preeclampsia, the other four pregnancy complications were associated with a significantly increased risk of UR after adjustment for risk factors (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e). After excluding women with previous caesarean deliveries, these associations were substantially elevated. Among women without previous caesarean delivery, the adjusted risk of UR was 1.41 (95% CI: 1.21\u0026ndash;1.65) for women with gestational diabetes mellitus, 5.03 (95% CI: 3.40\u0026ndash;7.42) for women with placental abruption, 5.38 (95% CI: 3.76\u0026ndash;7.70) for women with placenta previa, and 12.79 (95% CI: 7.69\u0026ndash;21.27) for women with placenta percreta (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab2\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eRisk of uterine rupture with pregnancy complications\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003ePregnancy complications \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eNo. UR\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eUR rate\u003csup\u003e#\u003c/sup\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eAdjusted UR rate\u003csup\u003e##\u003c/sup\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eaRR (95%CI): Model 1\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eaRR (95%CI): Model 2\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"8\" align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eAll women\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eNone\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e13,651\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.4\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.4\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1 (reference)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1 (reference)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePreeclampsia\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e338\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.7\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.5\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.97 (0.76\u0026ndash;1.24)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.825\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.89 (0.70\u0026ndash;1.14)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.358\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eGestational diabetes mellitus\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1,812\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3.2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.5\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.36 (1.16\u0026ndash;1.60)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.20 (1.03\u0026ndash;1.41)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.020\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePlacental abruption\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e175\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5.6\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5.4\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.44 (1.79\u0026ndash;3.33)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.74 (2.04\u0026ndash;3.66)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePlacenta previa\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e520\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6.4\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3.7\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.13 (1.64\u0026ndash;2.77)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.72 (1.33\u0026ndash;2.22)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePlacenta percreta\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e88\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e13.5\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6.2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3.81 (2.48\u0026ndash;5.83)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.64 (1.71\u0026ndash;4.07)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"8\" align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eWomen without previous caesarean delivery\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eNone\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1,808\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026ndash;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1 (reference)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1 (reference)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePreeclampsia\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e46\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026ndash;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.02 (0.69\u0026ndash;1.49)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.938\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.02 (0.69\u0026ndash;1.49)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.933\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eGestational diabetes mellitus\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e199\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.4\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026ndash;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.43 (1.22\u0026ndash;1.67)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.41 (1.21\u0026ndash;1.65)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePlacental abruption\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e46\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.9\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026ndash;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.98 (3.38\u0026ndash;7.34)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5.03 (3.40\u0026ndash;7.42)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePlacenta previa\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e116\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026ndash;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5.36 (3.76\u0026ndash;7.66)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5.38 (3.76\u0026ndash;7.70)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePlacenta percreta\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e25\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6.7\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026ndash;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e12.77 (7.69\u0026ndash;21.23)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e12.79 (7.69\u0026ndash;21.27)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003ctfoot\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"8\"\u003e\u003csup\u003e*\u003c/sup\u003e Each one of pregnancy complications has no other complications. None: Women with none of the five pregnancy complications.\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"8\"\u003e\u003csup\u003e#\u003c/sup\u003e Weighted uterine rupture rate per 1000 women\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"8\"\u003e\u003csup\u003e\u003cstrong\u003e##\u003c/strong\u003e\u003c/sup\u003e Weighted, and previous caesarean deliveries adjusted uterine rupture rate per 1000 women\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"8\"\u003e\u003csup\u003e\u003cstrong\u003ea\u003c/strong\u003e\u003c/sup\u003e Model 1: adjusted for sampling distribution of population and clustering of births within hospitals, region, hospital level, the number of antenatal visits, the women\u0026rsquo;s educational level, maternal age at delivery, parity, foetal presentation, gestational hypertension, chronic hypertension, heart disease, hepatic disease, severe anaemia, infection, thrombophlebitis, renal disease, lung disease, connective tissue disorders.\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"8\"\u003e\u003csup\u003e\u003cstrong\u003eb\u003c/strong\u003e\u003c/sup\u003e Model 2: adjusted for Model 1 as well as the number of previous caesarean deliveries (0, 1, \u0026ge;\u0026thinsp;2) and large for gestational age (yes/no).\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tfoot\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe results were similar after restricting the dataset to those women without advanced maternal age and multiple gravidities (Additional file Table S2). When women with offspring having abnormal foetal presentation and a birth weight of more than 4000 g were excluded, the risks of UR with pregnancy complications were largely unchanged (Additional file Table S3).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCo-occurrence of pregnancy complications and UR risk\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCompared with having none of the five pregnancy complications, having two or more complications was associated with a statistically significant almost 1.42\u0026ndash;fold risk of UR (Model 1, aRR: 1.88, 95% CI: 1.51\u0026ndash;2.34; Model 2, aRR: 1.42, 95% CI:1.14\u0026ndash;1.77).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRisk of UR in different gestational age groups\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFor a small proportion (14.9%, 2,531 of 16,949) of women with UR, the rupture occurred before term birth. An increased risk of UR before term birth was observed among women with gestational diabetes mellitus, placental abruption and placenta percreta (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). Women with placenta percreta had the highest risk of UR at 28 to 33 weeks gestation (Model 2, aRR: 6.21, 95% CI: 3.43\u0026ndash;11.24). The risk of UR among women with gestational diabetes mellitus was only observed at 34 to 36 weeks gestation (Model 2, aRR: 1.43, 95% CI: 1.03\u0026ndash;1.97). Moreover, the risk of UR among women with placenta previa was only observed at term (Model 2, aRR: 1.41, 95% CI: 1.08\u0026ndash;1.86).\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab3\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eAssociation between pregnancy complications and uterine rupture by gestational age group\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003ePregnancy complications \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth colspan=\"3\" align=\"left\"\u003e\n\u003cp\u003eGestational age group (week)\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eEarly preterm (28\u0026ndash;33)\u003c/strong\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eLate preterm (34\u0026ndash;36)\u003c/strong\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eTerm (\u0026ge;\u0026thinsp;37)\u003c/strong\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\" align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eNo. UR\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eNone\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e312\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1,430\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e11,909\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePreeclampsia\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e20\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e72\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e246\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eGestational diabetes mellitus\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e41\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e198\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1,573\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePlacental abruption\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e40\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e51\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e84\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePlacenta previa\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e46\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e138\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e336\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePlacenta percreta\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e16\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e11\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e61\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\" align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eUR rate\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e#\u003c/strong\u003e\u003c/sup\u003e \u003cstrong\u003e(Adjusted UR rate\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e##\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e)\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eNone\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.5 (2.5)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3.8 (3.4)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.3 (1.3)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePreeclampsia\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.0 (0.7)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.3 (1.7)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.7 (1.6)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eGestational diabetes mellitus\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.7 (3.4)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6.4 (4.3)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3.0 (2.3)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePlacental abruption\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6.6 (5.0)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e7.5 (5.7)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.6 (5.5)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePlacenta previa\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5.9 (3.5)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5.9 (3.0)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6.6 (4.1)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePlacenta percreta\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e46.0 (25.1)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e15.7 (6.0)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e10.9 (5.1)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\" align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eaRR (95%CI)\u003c/strong\u003e: \u003cstrong\u003eModel 1\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003ea\u003c/strong\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eNone\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1 (reference)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.72 (1.29\u0026ndash;2.30) \u003csup\u003e\u003cstrong\u003ec\u003c/strong\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.72 (0.57\u0026ndash;0.91) \u003csup\u003ed\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePreeclampsia\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.25 (0.14\u0026ndash;0.44) \u003csup\u003e\u003cstrong\u003ec\u003c/strong\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.78 (0.44\u0026ndash;1.38)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.89 (0.61\u0026ndash;1.31)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eGestational diabetes mellitus\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.29 (0.96\u0026ndash;1.73)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.84 (1.32\u0026ndash;2.57) \u003csup\u003e\u003cstrong\u003ec\u003c/strong\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.00 (0.75\u0026ndash;1.33)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePlacental abruption\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.69 (1.17\u0026ndash;2.46) \u003csup\u003ed\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.23 (1.62\u0026ndash;3.06) \u003csup\u003e\u003cstrong\u003ec\u003c/strong\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.85 (1.38\u0026ndash;2.50) \u003csup\u003e\u003cstrong\u003ec\u003c/strong\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePlacenta previa\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.27 (0.89\u0026ndash;1.82)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.34 (0.89\u0026ndash;2.03)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.91 (1.44\u0026ndash;2.53) \u003csup\u003e\u003cstrong\u003ec\u003c/strong\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePlacenta percreta\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e7.99 (4.43\u0026ndash;14.40) \u003csup\u003e\u003cstrong\u003ec\u003c/strong\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3.10 (1.65\u0026ndash;5.82) \u003csup\u003e\u003cstrong\u003ec\u003c/strong\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.52 (1.73\u0026ndash;3.69) \u003csup\u003e\u003cstrong\u003ec\u003c/strong\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\" align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eaRR (95%CI)\u003c/strong\u003e: \u003cstrong\u003eModel 2\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003eb\u003c/strong\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eNone\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1 (reference)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.47 (1.12\u0026ndash;1.92) \u003csup\u003ed\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.67 (0.53\u0026ndash;0.85) \u003csup\u003ed\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePreeclampsia\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.21 (0.12\u0026ndash;0.38) \u003csup\u003e\u003cstrong\u003ec\u003c/strong\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.63 (0.36\u0026ndash;1.12)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.77 (0.51\u0026ndash;1.14)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eGestational diabetes mellitus\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.13 (0.84\u0026ndash;1.53)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.43 (1.03\u0026ndash;1.97) \u003csup\u003ee\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.82 (0.62\u0026ndash;1.08)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePlacental abruption\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.60 (1.00\u0026ndash;2.31) \u003csup\u003ee\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.13 (1.55\u0026ndash;2.92) \u003csup\u003e\u003cstrong\u003ec\u003c/strong\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.12 (1.60\u0026ndash;2.81) \u003csup\u003e\u003cstrong\u003ec\u003c/strong\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePlacenta previa\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.08 (0.76\u0026ndash;1.54)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.97 (0.67\u0026ndash;1.43)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.41 (1.08\u0026ndash;1.86) \u003csup\u003ee\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePlacenta percreta\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6.21 (3.43\u0026ndash;11.24) \u003csup\u003e\u003cstrong\u003ec\u003c/strong\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.92 (0.99\u0026ndash;3.71)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.60 (1.08\u0026ndash;2.38) \u003csup\u003ee\u003c/sup\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003ctfoot\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\"\u003e\u003csup\u003e*\u003c/sup\u003e Each one of pregnancy complications has no other complications. None: Women with none of the five pregnancy complications.\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\"\u003e# Weighted uterine rupture rate per 1000 women\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\"\u003e\u003csup\u003e\u003cstrong\u003e##\u003c/strong\u003e\u003c/sup\u003e Weighted, and previous caesarean deliveries adjusted uterine rupture rate per 1000 women\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\"\u003e\u003csup\u003e\u003cstrong\u003ea\u003c/strong\u003e\u003c/sup\u003e Model 1: adjusted for sampling distribution of population and clustering of births within hospitals, region, hospital level, the number of antenatal visits, the women\u0026rsquo;s educational level, maternal age at delivery, parity, foetal presentation, gestational hypertension, chronic hypertension, heart disease, hepatic disease, severe anaemia, infection, thrombophlebitis, renal disease, lung disease, connective tissue disorders.\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\"\u003e\u003csup\u003e\u003cstrong\u003eb\u003c/strong\u003e\u003c/sup\u003e Model 2: adjusted for Model 1 as well as the number of previous caesarean deliveries (0, 1, \u0026ge;\u0026thinsp;2) and large for gestational age (yes/no).\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"4\"\u003e\u003cstrong\u003e\u003csup\u003ec\u0026nbsp;\u003c/sup\u003e\u003c/strong\u003e\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001;\u0026nbsp;\u003csup\u003ed\u003c/sup\u003e\u0026nbsp;\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01;\u0026nbsp;\u003csup\u003ee\u003c/sup\u003e\u0026nbsp;\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tfoot\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRole of large for gestational age\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe risk of UR in women with gestational diabetes mellitus without an LGA foetus was 1.18\u0026ndash;fold (Model 2, aRR: 1.18, 95% CI: 1.00\u0026ndash;1.38), and the risk was slightly larger in women with gestational diabetes mellitus and an LGA foetus (Model 2, aRR: 1.28, 95% CI: 1.09\u0026ndash;1.50) (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e). Among women at 34\u0026ndash;36 weeks gestational age, the association between gestational diabetes mellitus with an LGA foetus and UR was slightly elevated (Model 2, aRR: 1.40, 95% CI: 1.09\u0026ndash;1.79) (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab4\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eThe association between gestational diabetes mellitus and uterine rupture\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eGestational diabetes mellitus\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eNo. UR\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eUR rate\u003csup\u003e#\u003c/sup\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eAdjusted UR rate\u003csup\u003e##\u003c/sup\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eaRR (95%CI): Model 1\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eaRR (95%CI): model 2 \u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"8\" align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eAll women\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eNone only\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e12,138\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.4\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.5\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1 (reference)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1 (reference)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eNone and LGA\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1,513\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.7\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.02 (0.95\u0026ndash;1.11)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.550\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.96 (0.89\u0026ndash;1.04)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.335\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eGestational diabetes mellitus only\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1,452\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3.0\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.5\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.32 (1.11\u0026ndash;1.56)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.18 (1.00\u0026ndash;1.38)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.046\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eGestational diabetes mellitus and LGA\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e360\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.5\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.59 (1.34\u0026ndash;1.88)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.28 (1.09\u0026ndash;1.50)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.003\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"8\" align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eWomen at 34\u0026ndash;36 weeks gestational age\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eNone only\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1,274\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3.7\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1 (reference)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1 (reference)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eNone and LGA\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e156\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3.6\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.02 (0.81\u0026ndash;1.30)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.841\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.92 (0.73\u0026ndash;1.15)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.459\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eGestational diabetes mellitus only\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e140\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5.4\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.8\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.00 (0.81\u0026ndash;1.23)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.968\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.92 (0.76\u0026ndash;1.12)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.414\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eGestational diabetes mellitus and LGA\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e58\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e10.9\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6.5\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.77 (1.38\u0026ndash;2.26)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.40 (1.09\u0026ndash;1.79)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.009\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003ctfoot\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"8\"\u003e\u003csup\u003e*\u003c/sup\u003e Gestational diabetes mellitus: Women with no other four complications. None: Women with none of the five pregnancy complications. LGA: Large for gestational age.\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"8\"\u003e\u003csup\u003e\u003cstrong\u003e#\u003c/strong\u003e\u003c/sup\u003e Weighted uterine rupture rate per 1000 women\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"8\"\u003e\u003csup\u003e\u003cstrong\u003e##\u003c/strong\u003e\u003c/sup\u003e Weighted, and previous caesarean deliveries adjusted uterine rupture rate per 1000 women\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"8\"\u003e\u003csup\u003e\u003cstrong\u003ea\u003c/strong\u003e\u003c/sup\u003e Model 1: adjusted for sampling distribution of population and clustering of births within hospitals, region, hospital level, the number of antenatal visits, the women\u0026rsquo;s educational level, maternal age at delivery, parity, foetal presentation, gestational hypertension, chronic hypertension, heart disease, hepatic disease, severe anaemia, infection, thrombophlebitis, renal disease, lung disease, connective tissue disorders.\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"8\"\u003e\u003csup\u003e\u003cstrong\u003eb\u003c/strong\u003e\u003c/sup\u003e Model 2: adjusted for Model 1 as well as the number of previous caesarean deliveries (0, 1, \u0026ge;\u0026thinsp;2).\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tfoot\u003e\n\u003c/table\u003e\n\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eUsing data from more than 9\u0026nbsp;million singleton pregnant women in China, we found that approximately one-tenth of all women had pregnancy complications, and most occurred as single events. The incidence of UR varied in women with different single-complications, and the highest rate was observed in women with placenta percreta. Gestational diabetes mellitus, placental abruption, placenta previa and placenta percreta were associated with a substantially increased risk of UR, andthe risks for UR were 1- to 3-fold higher among women with these pregnancy complications. These associations persisted in women without previous caesarean delivery. Moreover, a significantly increased risk of UR before term birth was observed in women with gestational diabetes mellitus, placental abruption and placenta percreta. An LGA foetus increased the risk of UR in women with gestational diabetes mellitus, especially at 32 to 36 weeks gestation.\u003c/p\u003e \u003cp\u003eIn our data, the largest increased risk of UR was seen for placenta percreta (aRR: 2.64, 95% CI: 1.71\u0026ndash;4.07). Among women without previous caesarean delivery, the risk of UR was approximately 13 times higher in women with placenta percreta than in those without pregnancy complications (aRR: 12.79, 95% CI: 7.69\u0026ndash;21.27). A large retrospective cohort study from Negev found that pregnant women with placenta accreta spectrum disorders (including placenta percreta) had a significantly increased risk of UR (OR: 6.42, 95% CI: 2.0\u0026ndash;20.4)[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Moreover, previous research found that UR occurs in women without a history of caesarean section[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e] and identified spontaneous UR due to placenta percreta as occurring in a primigravida woman without prior uterine operation[\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. Thus, our findings are consistent with previous studies, suggesting that placenta percreta (especially without previous caesarean delivery) may increase the risk of UR.\u003c/p\u003e \u003cp\u003eTo date, few studies have reported the impact of other pregnancy complications on the occurrence of UR and have mainly focused on the impact of preeclampsia/eclampsia and diabetes mellitus. However, there are inconsistent conclusions regarding the effects of preeclampsia/eclampsia and gestational diabetes mellitus on UR risk. A population-based Negev study of 138 pregnant women with UR found that hypertension disorders (including preeclampsia/eclampsia) were associated with a twofold increased risk of UR (OR: 2.05, 95% CI: 1.20\u0026ndash;3.50), but diabetes mellitus (prepregnancy and gestation) was not related to the risk of UR (OR: 0.87, 95% CI: 0.41\u0026ndash;1.86)[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. However, this study was limited because the diagnoses of hypertension disorder and diabetes mellitus did not distinguish between different subtypes. In contrast, we found that gestational diabetes mellitus increased the risk of UR (aRR: 1.20, 95% CI: 1.03\u0026ndash;1.41), but preeclampsia did not increase the risk of UR (aRR: 0.89, 95% CI: 0.70\u0026ndash;1.14). Our finding is similar to results from two previous studies, where gestational diabetes increased the risk of UR (aOR: 5.78, 95% CI: 1.12\u0026ndash;20.00)[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e], and eclampsia was not related to the risk of UR (aOR: 0.08, 95% CI: 0.01\u0026ndash;0.71)[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eFurthermore, we found that approximately six percent of women had two or more pregnancy complications. A previous study identified placenta previa as often occurring alongside placenta accreta, leading to a higher incidence of bleeding complications[\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. Moreover, placental abruption concurrently presents with preeclampsia in the same pregnancy, and these two complications have a similar pathogenesis, such as placental ischaemia[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. The cooccurrence of preeclampsia and placental abruption was associated with worse maternal, foetal and neonatal outcomes (e.g., stillbirth/neonatal deaths)[\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. However, the combined effect of pregnancy complications on the risk of UR has been less closely studied. Our results indicate that having two or more pregnancy complications may increase the risk of UR (Model 2, aRR: 1.42, 95% CI: 1.14\u0026ndash;1.77), but we failed to assess the effects of unique combinations due to small samples.\u003c/p\u003e \u003cp\u003eThe pathophysiological mechanism underlying the relationship between pregnancy complications and the occurrence of UR remains unclear. The occurrence of UR may be directly or indirectly caused by a weak myometrium and excessive expansion of the uterine cavity. We speculate that the increased risk of UR may be due to pregnancy complications themselves through a specific mechanism. For example, UR from placenta percreta occurs because the placental villi invade the myometrium at the site of placental implantation (particularly at a previous scar site), resulting in UR[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. In our study, we found that placenta percreta was still associated with an increased risk of UR in women without previous caesarean delivery. The possible reason for this might be the thinning of the uterus after multiple induced abortions, resulting in placental percreta leading to UR. In addition, we hypothesize that pregnancy complications may indirectly increase the occurrence of UR by increasing the occurrence of certain obstetric complications. Our results support the hypothesis that gestational diabetes mellitus in combination with LGA may increase the risk of UR. In our study, we found that the association between gestational diabetes mellitus without an LGA foetus and UR was 1.18\u0026ndash;fold (Model 2, aRR: 1.18, 95% CI: 1.00\u0026ndash;1.38), and the risk of UR was slightly larger in women with gestational diabetes mellitus and an LGA foetus (especially at 34\u0026ndash;36 weeks gestational age). Our findings raise the possibility that UR may occur during late pregnancy among diabetic women, when excess foetal growth leads to excessive expansion of the uterine cavity. Future research is required to investigate the mechanism of pregnancy complications on the occurrence of UR.\u003c/p\u003e \u003cp\u003eUR often occurs before or during labour without warning. The risk of UR can increase in the presence of predisposing factors, such as a history of caesarean section and its related pregnancy complications. Clinicians may tend to focus on women with a history of caesarean delivery, ignoring those without such a history but with complications during pregnancy. Current guidelines developed by the American College of Obstetricians and Gynaecologists (ACOG) and Royal College of Obstetricians and Gynaecologists (RCOG) place a strong emphasis on the impact of vaginal trial delivery after caesarean section on UR[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Unfortunately, there is currently a lack of guidelines for pregnant women with pregnancy complications to prevent the occurrence of UR. For example, current guidelines developed by the ACOG only recommend that women with gestational diabetes mellitus should be counselled regarding the risks and benefits of a scheduled caesarean delivery when the estimated foetal weight is 4,500 g or more[\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. In our study, we found that an LGA foetus (especially at 34\u0026ndash;36 weeks gestational age) was associated with an increased risk of UR in women with gestational diabetes mellitus. Our findings suggest that controlling weight throughout pregnancy for women with gestational diabetes mellitus may play an important role in preventing the occurrence of UR. Additionally, we found that UR occurred only at term for women with placenta previa. Our findings support the recommendation that women with uncomplicated placenta previa should have a planned delivery at 36\u0026ndash;-37 weeks of gestation to avoid haemorrhage[\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. Moreover, evidence has shown that an accurate prenatal diagnosis and a standardized multidisciplinary team approach improve the pregnancy outcomes of women with placenta percreta[\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. Thus, standardized protocols for prenatal diagnosis and management of pregnancy complications should be established throughout pregnancy to reduce the occurrence of UR.\u003c/p\u003e \u003cp\u003eOur study has a number of strengths. First, we used common protocols to collect data through uniformly trained clinicians, so the data quality was high. Second, the large sample size allowed us to analyse the risk of UR with pregnancy complications in several subgroups. Third, we were able to adjust for several potential confounders (e.g., the number of previous caesarean deliveries, LGA, abnormal foetal presentation, advanced maternal age, multiple gravidities, coexisting comorbidity, etc. ).\u003c/p\u003e \u003cp\u003eWe acknowledge some limitations within this study. First, there may be a possibility of the underreporting of pregnancy complications in our retrospective study. Additionally, some women with pregnancy complications may lost to follow up, when they abandoned treatment or were transferred to other non-monitoring hospitals. However, some women with pregnancy complications may also be transferred from other non-monitoring hospitals into monitoring hospitals in the NMNMSS. Second, we were unable to obtain several variables that may have been related to the occurrence of UR, including information on the intended mode of delivery[\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e], the interval between this pregnancy and the last caesarean section[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e], and the history of other uterine operations (e.g., myomectomy)[\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e]. Third, there was a lack of information on the duration and severity of pregnancy complications in our study, and there may be deviations in evaluating the impact of pregnancy complications on the risk of UR. Fourth, we did not distinguish between complete and partial UR[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e], so we could not analyse the influence of pregnancy complications on the different types of UR. Therefore, the estimation of UR risk may be biased.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eOur study identified that gestational diabetes mellitus, placental abruption, placenta previa and placenta percreta increased the risk of UR. An increased risk of UR before term birth was observed among women with gestational diabetes mellitus, placental abruption and placenta percreta. Furthermore, an LGA foetus increased the risk of UR in women with gestational diabetes mellitus, especially at 32 to 36 weeks gestation. Thus, physicians should provide early, better antenatal care and intervention for women with these high-risk pregnancy complications.\u003c/p\u003e "},{"header":"Abbreviations","content":"\u003cp\u003eNMNMSS: National Maternal Near Miss Surveillance System; UR: uterine rupture; LGA: large for gestational age; HELLP:haemolysis, elevated liver enzymes and low platelets; OGTT: oral glucose tolerance test; aRR: adjusted relative risk; CI: confidence Interval; ACOG: American College of Obstetricians and Gynaecologists; RCOG: Royal College of Obstetricians and Gynaecologists\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe thank the institutions and staff of the National Maternal Near Miss Surveillance System\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eJT, JL and JZ conceived the study. YM and YX X managed the dataset and PR C conducted the analyses. JT wrote the first draft of the manuscript. All authors provided intellectual input and contributed and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study has received funding by The National Key Research and Development Program of China (2018YFC1002200), The Sichuan province Key Research and Development Program of China (No. 2019YFS0530).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was approved by the Ethics Review Committee of West China Second University Hospital, Sichuan University(Protocol ID: 2012008; date of approval: 3 March 2012), and conducted in accordance with the principles of the Declaration of Helsinki. Because of the retrospective design of this study, the Ethics Review Committee of West China Second University Hospital, Sichuan University has waived the requirement of the informed consent for this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors have read and approved the content, and agree to submit it for consideration for publication in your journal.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eKaczmarczyk M, Spar\u0026eacute;n P, Terry P, Cnattingius S. Risk factors for uterine rupture and neonatal consequences of uterine rupture: a population-based study of successive pregnancies in Sweden. 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Am J Obstet Gynecol. 2018;218:75\u0026ndash;87.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhu L, Zhang R, Zhang S, Shi W, Yan W, Wang X, et al. Chinese neonatal birth weight curve for different gestational age. Zhonghua Er Ke Za Zhi. 2015;53:97\u0026ndash;103.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWilliams R. Using the Margins Command to Estimate and Interpret Adjusted Predictions and Marginal Effects. The Stata Journal. 2012;12:308\u0026ndash;31.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAbebe F, Mannekulih E, Megerso A, Idris A, Legese T. Determinants of uterine rupture among cases of Adama city public and private hospitals, Oromia, Ethiopia: a case control study. Reprod Health. 2018;15:161.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAl-Zirqi I, Daltveit AK, Fors\u0026eacute;n L, Stray-Pedersen B, Vangen S. Risk factors for complete uterine rupture. American Journal of Obstetrics and Gynecology. 2017;216:165.e1-165.e8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFadl HE, \u0026Ouml;stlund IKM, Magnuson AFK, Hanson USB. Maternal and neonatal outcomes and time trends of gestational diabetes mellitus in Sweden from 1991 to 2003. Diabetic Medicine. 2010;27:436\u0026ndash;41.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eThisted DLA, Mortensen LH, Krebs L. Uterine rupture without previous caesarean delivery: a population-based cohort study. European Journal of Obstetrics \u0026amp; Gynecology and Reproductive Biology. 2015;195:151\u0026ndash;5.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFitzpatrick KE, Kurinczuk JJ, Alfirevic Z, Spark P, Brocklehurst P, Knight M. Uterine Rupture by Intended Mode of Delivery in the UK: A National Case-Control Study. PLoS Med. 2012;9:e1001184.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKinoshita T, Ogawa K, Yasumizu T, Kato J. Spontaneous rupture of the uterus due to placenta percreta at 25-weeks\u0026rsquo; gestation: a case report. J Obstet Gynaecol Res. 1996;22:125\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eUsta IM, Hobeika EM, Abu Musa AA, Gabriel GE, Nassar AH. Placenta previa-accreta: Risk factors and complications. American Journal of Obstetrics and Gynecology. 2005;193:1045\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHan M, Liu D, Zeb S, Li C, Tong M, Li X, et al. Are maternal and neonatal outcomes different in placental abruption between women with and without preeclampsia? Placenta. 2019;85:69\u0026ndash;73.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAmerican College of Obstetricians and Gynaecologists., A, B, C, D, E, et al. ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus. Obstet Gynecol. 2018;131:e49\u0026ndash;64.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSpong CY, Mercer BM, D\u0026rsquo;Alton M, Kilpatrick S, Blackwell S, Saade G. Timing of Indicated Late-Preterm and Early-Term Birth. Obstetrics \u0026amp; Gynecology. 2011;118:323\u0026ndash;33.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShamshirsaz AA, Fox KA, Salmanian B, Diaz-Arrastia CR, Lee W, Baker BW, et al. Maternal morbidity in patients with morbidly adherent placenta treated with and without a standardized multidisciplinary approach. American Journal of Obstetrics and Gynecology. 2015;212:218.e1-218.e9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVandenberghe G, Bloemenkamp K, Berlage S, Colmorn L, Deneux-Tharaux C, Gissler M, et al. The International Network of Obstetric Survey Systems study of uterine rupture: a descriptive multi-country population-based study. BJOG: Int J Obstet Gy. 2019;126:370\u0026ndash;81.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGetahun WT, Solomon AA, Kassie FY, Kasaye HK, Denekew HT. Uterine rupture among mothers admitted for obstetrics care and associated factors in referral hospitals of Amhara regional state, institution-based cross-sectional study, Northern Ethiopia, 2013\u0026ndash;2017. PLoS ONE. 2018;13:e0208470.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-pregnancy-and-childbirth","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"prch","sideBox":"Learn more about [BMC Pregnancy and Childbirth](http://bmcpregnancychildbirth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/prch/default.aspx","title":"BMC Pregnancy and Childbirth","twitterHandle":"@BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Pregnancy complications, Uterine rupture, Risk factors, Large for gestational age, Preterm delivery","lastPublishedDoi":"10.21203/rs.3.rs-424294/v2","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-424294/v2","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground:\u003c/strong\u003e The goal of this study was to investigate whether pregnancy complications are associated with an increased risk of uterine rupture (UR) and how that risk changes with gestational age.\u003cstrong\u003e \u003c/strong\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eMethods: \u003c/strong\u003eWe obtained all data from China’s National Maternal Near Miss Surveillance System (NMNMSS) between 2012 and 2018. Poisson regression analysis was used to assess the risk of UR with pregnancy complications (preeclampsia, gestational diabetes mellitus, placental abruption, placenta previa and placenta percreta) among 9,454,239 pregnant women. Furthermore, we analysed the risks of UR with pregnancy complications in different gestational age groups.\u003cstrong\u003e \u003c/strong\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e Compared with women without pregnancy complications, those with different complications (except for preeclampsia) had a 1- to 3-fold greater risk of UR. These associations also persisted in women without a previous caesarean delivery. Moreover, an increased risk of UR before term birth was observed among women with gestational diabetes mellitus, placental abruption and placenta percreta. A large for gestational age (LGA) foetus increased the risk of UR in women with gestational diabetes mellitus, especially at 32 to 36 weeks gestation. \u003c/p\u003e\u003cp\u003e\u003cstrong\u003eConclusions: \u003c/strong\u003eBetter quality antenatal care and early intervention for women with these pregnancy complications are needed to minimize the incidence of UR.\u003c/p\u003e","manuscriptTitle":"Pregnancy Complications and Risk of Uterine Rupture Among Women With Singleton Pregnancies in China","msid":"","msnumber":"","nonDraftVersions":[{"code":2,"date":"2021-10-08 15:19:37","doi":"10.21203/rs.3.rs-424294/v2","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major revision","date":"2021-11-24T11:12:02+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2021-10-24T19:39:47+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"54a20210-51fa-45a2-866a-7b9e456f37bf","date":"2021-10-13T19:00:01+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"8c68e0fd-41cf-46de-9136-2c20e7c06974","date":"2021-09-24T12:05:05+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2021-09-21T10:22:55+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2021-09-21T10:19:15+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2021-09-15T08:49:35+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2021-09-15T08:45:42+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Pregnancy and Childbirth","date":"2021-09-08T15:44:29+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-pregnancy-and-childbirth","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"prch","sideBox":"Learn more about [BMC Pregnancy and Childbirth](http://bmcpregnancychildbirth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/prch/default.aspx","title":"BMC Pregnancy and Childbirth","twitterHandle":"@BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"ed172517-3cce-4fe4-b9eb-8dd649aa2316","owner":[],"postedDate":"October 8th, 2021","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":7718332,"name":"Maternal \u0026 Fetal Medicine"}],"tags":[],"updatedAt":"2022-02-16T18:48:47+00:00","versionOfRecord":{"articleIdentity":"rs-424294","link":"https://doi.org/10.1186/s12884-022-04465-w","journal":{"identity":"bmc-pregnancy-and-childbirth","isVorOnly":false,"title":"BMC Pregnancy and Childbirth"},"publishedOn":"2022-02-16 18:48:47","publishedOnDateReadable":"February 16th, 2022"},"versionCreatedAt":"2021-10-08 15:19:37","video":"","vorDoi":"10.1186/s12884-022-04465-w","vorDoiUrl":"https://doi.org/10.1186/s12884-022-04465-w","workflowStages":[]},"version":"v2","identity":"rs-424294","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-424294","identity":"rs-424294","version":["v2"]},"buildId":"FbvkV6FR0MCFSLy54lSbu","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}