Risk Factors and Perinatal Outcomes for Placenta Praevia at Delivery in nulliparas: a Retrospective Case-control Study

Risk Factors and Perinatal Outcomes for Placenta Praevia at Delivery in nulliparas: a Retrospective Case-control Study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Risk Factors and Perinatal Outcomes for Placenta Praevia at Delivery in nulliparas: a Retrospective Case-control Study Xuemin Wei, Mi Xiang, Weiwei Cheng This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5339162/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background Placenta previa leads to dangerous obstetrical outcomes, including obstetrical hemorrhage and preterm birth, and its rate is still increasing.The objective is to analyze the risk factors for placenta previa in nulliparas population, and to observe the perinatal outcomes of these patients. Methods This retrospective analysis was conducted at the International Peace Maternity and Child Health Hospital, China, from January 2018 to December 2022. The placenta previa group consisted of 464 nulliparas with placenta previa at delivery. For each placenta previa patients, 4 nulliparas without placenta previa who gave birth on the same day were randomly selected as the control group (n = 1856). Multivariable logistic regression were employed for adjusted analyses to identify risk factors for placenta previa. Stratified analysis by assisted reproductive techniques(ART) was used to exclude confounders. Furthermore, maternal and neonatal outcomes were compared between the two groups. Results Among 68,310 deliveries included in the analysis, 464 (0.68%) nulliparas with singleton pregnancy of these women had placenta previa at delivery. Histories of endometriosis [Adjusted Odds Ratio (aOR) 5.50], ART [aOR 2.70], and advanced maternal age [aOR 1.81] emerged as significant risk factors for placenta previa. Stratified analysis showed endometriosis linked to placenta previa both in ART [aOR 2.25] and natural conceptions [aOR 7.69], significantly raising spontaneous pregnancy risk. Notably, the placenta previa group exhibited a significantly higher proportion of maternal and neonatal adverse outcomes compared to the control group (P < 0.05). Conclusions In nulliparas, endometriosis, ART, and advanced maternal age emerge as independent risk factors for placenta previa at delivery, leading to adverse perinatal outcomes. In addition, endometriosis history was significantly associated with placenta previa in ART and natural conceptions, increasing risk for spontaneous pregnancies. Placenta previa Nulliparas pregnancy History of endometriosis Assisted reproductive techniques Perinatal outcome Risk factors Background Placenta previa (PP) is the complete or partial covering of the internal os of the cervix with the placenta after the 28th week of gestation[ 1 ]. In recent years, the occurrence of PP has gradually increased, which coincides with the rising rates of cesarean sections[ 2 ], abortions[ 3 ], and uterine surgical procedures[ 4 ]. This trend translates to an estimated incidence of PP in approximately 1 out of every 200 to 250 live births[ 5 ]. PP poses a significantly increased risk of dangerous complications, including obstetrical hemorrhage[ 6 ] and preterm birth[ 7 ]. In severe cases, it can cause hemodynamic instability such as disseminated intravascular coagulation(DIC), necessitating immediate surgery, blood transfusion, or hysterectomy, potentially resulting in infertility, or even death[ 8 , 9 , 10 ]. The well-documented risk factors for PP are assisted reproductive techniques (ART) [ 11 ], history of intrauterine surgeries[ 4 ], and prior cesarean delivery[ 12 ]. However, the exact etiology and pathogenesis of PP remain unclear so far. Additionally, there is a lack of sufficient research into risk factors for PP at delivery in nulliparas population. Therefore, this study aims to explore risk factors associated with PP at delivery in nulliparas pregnancy and to observe neonatal outcomes among affected individuals. Methods Study setting and participants This retrospective case-control study was conducted at the International Peace Maternity and Child Health Hospital (IPMCHH), a single tertiary referral medical center of Shanghai, east China, from January 1st, 2018 to December 31st, 2022. During this period, women delivered in our hospital had demographic and clinical data prospectively collected throughout pregnancy. Due to the retrospective nature of the study, patients were informed and signed informed consent forms at their first antenatal visit at IPMCHH, a teaching hospital for Shanghai JiaoTong University School of Medicine. This study was approved by the Ethics Committee of the International Peace Maternity and Child Health Hospital, in accordance with the Helsinki declaration. Inclusion and exclusion criteria Inclusion criteria: (1) 28 weeks ≤ pregnancy time ≤ 41 weeks; (2) nulliparas with singleton pregnancy;(3) cesarean section to termination pregnancy; (4) complete case information; (5) meets the diagnostic criteria for PP. Exclusion criteria: (1) patients with previous history of cesarean section, or pregnancy; (2) women whose pregnancies were terminated or who delivered before 28 weeks; (3) no placenta previa at delivery; (4) twin pregnancy;(5) incomplete case information;(6) patients with hematologic disorders, malignant tumors, or infectious diseases. Finally, a total of 464 nulliparas with singleton pregnancy complicated PP were grouped in the PP group. For each PP participant, 4 nulliparas without PP who gave birth on the same day were randomly selected as the control group (n = 1856). Clinical data collection Data in the perinatal database is documented by attending physicians after delivery. Medical secretaries review the information before entry. Coding is done after evaluating prenatal care records and hospital documents. This ensures completeness and accuracy. The database includes demographic information, perinatal assessments, maternal morbidities, and newborns outcomes. Records are anonymized before analysis. The hospitalization database includes demographic information and International Classification of Diseases, ninth revision codes(ICD-9) for all diagnoses. Demographic information includes maternal age, gestational week, history of endometriosis, ART, pregnancy comorbidities (chronic hypertension, pregestational diabetes, hypothyroidism), pre-pregnancy body mass index (BMI). Perinatal outcomes such as maternal related indicators (amount of postpartum bleeding, the rate of postpartum hemorrhage(PPH) and placenta adherence), and neonatal condition (birth week, birth weight, Apgar score at 5 min after birth) were also counted in both groups. Diagnostic criteria for PP at delivery: placenta previa at delivery was identified when it was an indication for cesarean delivery in study participants. Placenta attached to the lower uterine segment reaching or covering the internal cervical os at delivery; also, intraoperative diagnosis based on the position of the placenta. Maternal age is defined as age in completed years at delivery. Advanced maternal age is defined as an age ≥ 35 years on the estimated date of delivery. BMI was calculated by using self-reported prepregnancy weight and height values (weight/height 2 , kg/m 2) . Diagnosis of endometriosis was based on laparoscopy (gold standard), a history of surgical treatments such as cystectomy for ovarian endometriosis, ablation or excision of endometriotic implants, and adhesiolysis. PPH is defined as bleeding ≥ 1000 mL after delivery in 24 hours. ART includes: in vitro fertilization-embryo transfer (IVF), frozen embryo transfer and intracytoplasmic sperm injection(ICSI), but does not include intrauterine insemination from donor(IUI D), intrauterine insemination from spouse(IUI S) and other medically assisted reproduction: oocyte donation, fertility preservation, gestational carriers which are forbidden in China. Statistical Methods Continuous variables are expressed as the mean ± standard deviation and were evaluated using the t-test. Categorical variables are expressed as rates and were evaluated using the χ2 test, corrected χ2 test or Fisher’s exact test, as appropriate. Those data that did not meet normal distribution or equal variance were presented as median [M (P25, P75)], the Mann-Whitney U test was used for comparisons between two groups, and the Kruskal-Wallis rank sum test was used for comparisons between multiple independent samples. Univariate and multivariate logistic regression analyses were used to explore the risk factors of PP. Multivariate analysis was performed using binary logistic regression analysis. Stratified analysis was further analyzed to exclude confounders. To investigate ART's influence on the association between endometriosis and PP, we stratified the analysis by ART use. Missing data were not imputed.Statistical analysis was performed using SPSS 27.0 software (IBM Corp., Armonk, NY). All tests were two-sided, and p < 0.05 was considered as statistically significant. Results During the study period, 68,310 women delivered at our hospital. Among them, 34,967 were nulliparas with singleton pregnancy, and 464 (0.68%) of these women were complicated with PP at delivery. Compared to the control group, the women in the PP group were older [32.72 ± 4.04 vs 30.99 ± 3.65, P < 0.001] and had significantly higher proportions of endometriosis history [16.2% vs 2.7%, P < 0.001], ART use [28.0% vs 10.1%, P < 0.001], intrauterine surgery history [9.5% vs 5.7%,P = 0.003], and abortion surgery history [35.1% vs 29.3%, P = 0.015] (Table 1 ). There were no statistically significant differences between the two groups in terms of chronic hypertension, pregestational diabetes, hypothyroidism, pre-pregnancy BMI (P > 0.05,Table 1 ). Table 1 Demographics characteristics of placenta previa group and non-placenta previa group Maternal characteristics Placenta previa (n = 464) Non-Placenta previa (n = 1856) P value Maternal age (y) 32.72 ± 4.04 30.99 ± 3.65 < 0.001 BMI category BMI < 28 453(97.6%) 1776(95.7%) 0.054 BMI ≧ 28 11(2.4%) 80(4.3%) Smoker 0 0 - Use of ART YES 130(28.0%) 188(10.1%) < 0.001 NO 334(72.0%) 1668(89.9%) History of endometriosis YES 75(16.2%) 51(2.7%) < 0.001 NO 389(83.8%) 1804(97.3%) History of abortions YES 163(35.1%) 544(29.3%) 0.015 NO 301(64.9%) 1312(70.7%) History of hysteroscopic surgery YES 44(9.5%) 106(5.7%) 0.003 NO 419(90.5%) 1750(94.3%) Chronic hypertension YES 14(3.0%) 44(2.4%) 0.425 NO 450(97.0%) 1812(97.6%) Pregestational diabetes YES 19(4.1%) 50(2.7%) 0.112 NO 445(95.9%) 1806(97.3%) Hypothyroidism YES 58(12.5%) 191(10.3%) 0.169 NO 406(87.5%) 1665(89.7%) Maternal age is defined as age in completed years at delivery. BMI, pre-pregnancy body mass index was calculated by using self-reported prepregnancy weight and height values (weight/height 2 , kg/m 2 ). Smoker: Smoked tobacco before pregnancy or during pregnancy. ART, Assisted reproduction technology includes: In vitro fertilization-embryo transfer (IVF), frozen embryo transfer and Intracytoplasmic sperm injection(ICSI), but does not include Intrauterine insemination from donor(IUI D), Intrauterine insemination from spouse(IUI S) and other medically assisted reproduction: Oocyte donation, fertility preservation, gestational carriers which are forbidden in China. Adjusted odds ratios of risk factors for PP are described in Table 2 . The presence or absence of PP was used as the dependent variable, and the indicators that differed in the univariate analysis, such as maternal age, history of endometriosis, ART, history of intrauterine surgery, history of abortion surgery were used as independent variables into a multifactorial logistic regression model. The results showed that advanced maternal age (aOR,1.81, 95%CI,1.40–2.33), history of endometriosis (aOR, 5.50, 95% CI, 3.73–8.10) and application of ART (aOR, 2.70, 95% CI,2.02–3.61) were independent risk factors for PP at delivery (P < 0.05, Table 2 ). Table 2 Adjusted odds ratios of factors associated with placenta previa Univariate analysis Multivariate logistic regression Indicators OR(95% CI) P value aOR(95% CI) P value Maternal age ≥ 35(y) 2.46(1.95–3.10) < 0.001 1.81(1.40–2.33) < 0.001 BMI ≥ 28 0.54(0.29–1.02) 0.048 0.53(0.27–1.02) 0.057 ART 3.45(2.68–4.45) < 0.001 2.70(2.02–3.61) < 0.001 History of endometriosis 6.82(4.70–9.89) < 0.001 5.50(3.73–8.10) < 0.001 History of abortions 1.31(1.05–1.62) 0.015 1.21(0.97–1.52) 0.099 History of hysteroscopic surgery 1.73(1.20–2.50) 0.003 0.83(0.54–1.27) 0.396 Chronic hypertension 1.28(0.69–2.36) 0.426 - - Pregestational diabetes 1.54(0.90–2.64) 0.115 - - Hypothyroidism 1.25(0.91–1.70) 0.170 - - OR: Odds Ratio; aOR: adjusted Odds Ratio; Maternal age is defined as age in completed years at delivery. BMI, pre-pregnancy body mass index was calculated by using self-reported prepregnancy weight and height values (weight/height 2 , kg/m 2 ). ART, Assisted reproduction technology includes: In vitro fertilization-embryo transfer (IVF), frozen embryo transfer and Intracytoplasmic sperm injection(ICSI), but does not include Intrauterine insemination from donor(IUI D), Intrauterine insemination from spouse(IUI S) and other medically assisted reproduction: Oocyte donation, fertility preservation, gestational carriers which are forbidden in China. Tables 3.1 and 3.2 outline the risk factors for developing PP by stratified analysis by ART use. Using stepwise model selection in multifactorial logistic regression model, the following 2 factors remained statistically significant in ART subgroup: advanced maternal age (aOR, 1.66; 95% CI, 1.03–2.66), history of endometriosis (aOR, 2.25; 95% CI,1.15–4.42) (P < 0.05, Table 3.1 ). Similarly, the following 3 factors remained statistically significant in natural conception subgroup: advanced maternal age (aOR, 1.84; 95%CI,1.36–2.48), history of endometriosis (aOR,7.69; 95%CI,4.85–12.18) and history of abortion (aOR,1.36; 95%CI,1.05–1.76)(P < 0.05, Table 3.2 ). Table 3.1 Stratified analysis by ART, univariate analysis for PP in ART subgroup ( n = 318) and natural conception subgroup (n = 2002) ART subgroup ( n = 318) Natural conception subgroup (n = 2002) Indicators OR (95% CI) P value OR (95% CI) P value Advanced maternal age ≥ 35(y) 1.64(1.04–2.57) 0.032 2.08(1.56–2.77) < 0.001 BMI ≥ 28 0.13(0.02–0.98) 0.058 0.72(0.37–1.40) 0.330 History of endometriosis 2.52(1.30–4.86) 0.006 8.26(5.24–13.02) < 0.001 History of abortions 0.74(0.45–1.19) 0.214 1.51(1.18–1.93) < 0.001 History of hysteroscopic surgery 0.79(0.48–1.33) 0.384 1.18(0.62–2.24) 0.609 Chronic hypertension 0.57(0.17–1.84) 0.344 1.48(0.73–3.03) 0.280 Pre-gestational diabetes 3.51(0.89–13.83) 0.073 1.29(0.67–2.45) 0.446 hypothyroidism 1.36(0.70–2.65) 0.364 1.17(0.81–1.69) 0.418 Table 3.2 Multivariate logistic regression for PP in ART subgroup ( n = 318) and natural conception subgroup (n = 2002) ART subgroup ( n = 318) Natural conception subgroup (n = 2002) Indicators aOR (95% CI) P value aOR (95% CI) P value Advanced maternal age ≥ 35(y) 1.66(1.03–2.66) 0.036 1.84(1.36–2.48) < 0.001 History of endometriosis 2.25(1.15–4.42) 0.013 7.69(4.85–12.18) < 0.001 History of abortions NA NA 1.36(1.05–1.76) 0.020 OR: Odds Ratio; aOR: adjusted Odds Ratio; Advanced maternal age is defined as age ≥ 35 years in completed years at delivery. BMI was calculated by using self-reported prepregnancy weight and height values (weight/height 2 , kg/m 2 ). ART, Assisted reproduction technology includes: In vitro fertilization-embryo transfer (IVF), frozen embryo transfer and Intracytoplasmic sperm injection(ICSI), but does not include Intrauterine insemination from donor(IUI D), Intrauterine insemination from spouse(IUI S) and other medically assisted reproduction: Oocyte donation, fertility preservation, gestational carriers which are forbidden in China. Table 4 describes pregnancy outcomes of placenta previa group and non-placenta previa group. Those with PP at delivery were more likely to have decreased gestational age at delivery (median, 37 weeks [32–40] vs 39 weeks [29–41];P < .0001), higher rate of preterm delivery at < 37 weeks’ gestation (24.78% vs 5.82%;P < .0001), more intraoperative bleeding volume (424.58 ± 343.64 vs 224.41 ± 82.32;P < .0001), more placenta adherence (22.63% vs 4.74%;P < .0001) and lower neonatal birthweight (3025.26 ± 439.08 vs 3307.03 ± 492.49; P = 0.01,Table 4 ). There were no differences in the following outcomes: stillbirth, NICU admission, 5-minute Apgar score 0.05,Table 4 ). Table 4 Pregnancy outcomes of placenta previa group and Non-placenta previa group Pregnancy outcomes Placenta previa N = 464 Non-placenta previa N = 1856 P value Maternal outcomes Gestational age (weeks) 37(32–40) 39(29–41) 0.031 Preterm delivery (< 37 week) 115(24.78%) 108(5.82%) < 0.001 Intraoperative bleeding volume(ml) 424.58 ± 343.64 224.41 ± 82.32 < 0.001 PPH 30(6.47%) 4(0.22%) < 0.001 Placenta adherence 105(22.63%) 88(4.74%) 0.99 Neonatal birthweight (g) 3025.26 ± 439.08 3307.03 ± 492.49 0.012 Low Neonatal birthweight 47(10.13%) 98(5.28%) < 0.001 Neonatal Sex Male 235(50.65%) 1016(54.74%) 0.113 Female 229(49.35%) 840(45.26%) 5-min Apgar < 7 8(1.72%) 27(1.45%) 0.670 NICU admission 6(1.30%) 22(1.20%) 0.849 Neonatal death 0 0 - Preterm delivery :Defined as birth before completed weeks of gestation. PPH: Postpartum hemorrhage, defined as ≥ 1000 mL during the 24 h after delivery. Placenta adherence:Pathological adhesion or implantation of placenta, unable to be naturally peeled off, requiring manual peeling. Low Neonatal birthweight :defined as a neonate whose birth weight < 2500g. NICU admission : Admission to neonatal intensive care unit from the delivery room or maternity ward. Discussion In this study, PP incidence was 0.68% in nulliparas at delivery. Compared to the control group, PP patients were older and had higher rates of endometriosis, ART use, intrauterine surgery, and abortion. After adjusting analysis by multivariate logistic regression, the 3 statistically significant risk factors for PP at delivery were endometriosis, ART use, and advanced maternal age. Stratified analysis showed endometriosis linked to PP in both ART group and natural conceptions, especially raising spontaneous pregnancy risk. Additionally, nulliparas with PP faced higher risks of preterm birth, hemorrhage and placenta adherence, but no significant differences in stillbirth, NICU admission, Apgar scores, or neonatal/maternal death. This study showed endometriosis history was an independent risk factor for PP in nulliparas, those with endometriosis history had 5.50 times higher risk than those without. Meta-analysis revealed that endometriosis showed higher risk of PP, with odds ratio of 3.03–3.31[ 13 , 14 ], and preterm delivery[ 15 ]. Endometriosis history remains a risk factor for PP even after adjusting for other parameters[ 16 ], maternal age, ART, multiplicity, and previous deliveries did not alter these differences[ 17 ]. This aligns with our study's key findings. Moreover, Farella M et al[ 18 ] reported that independent factors associated with PP include conception via ART and a history of stage III or IV endometriosis. Women with deep endometriosis have a higher risk of PP[ 19 ]. Additionally, in this study, stratified analysis showed that endometriosis history was significantly associated with PP in both ART and natural conceptions subgroup, posing an elevated risk for spontaneous pregnancies. Similarly, previous studies[ 20 , 21 ] found endometriosis raised PP risk, independent of medically assisted reproduction, with a slight risk increase in spontaneous pregnancies. Compared to non-endometriosis women with non-ART pregnancies, PP risk was higher in both endometriosis women with or without ART [No endo/ART (aRR 2.26, 99% CI 1.42–3.60), Endo/no ART (aRR 1.66, 99% CI 1.18–2.33)][ 22 ]. Our study focused on nulliparas women, excluding cesarean history, is congruent with these findings. These results indicate endometriosis women, including ART users, need heightened pregnancy surveillance and management. However, the pathogenesis of PP remains unclear. Reasons may include pelvic adhesions, abnormal uterine position, limited uterine mobility, or abnormal uterine contractions, causing placenta displacement. Endometriosis can alter endometrial properties and affect placental implantation. Adequate progesterone levels regulate the endometrium, and endometriosis can induce progesterone resistance, leading to PP[ 5 ]. Therefore, the exact pathogenesis of PP needs further research to clarify. Our study found that nulliparas conceiving via ART had increased risk of PP at delivery. Previous study[ 23 ] similarly observed a significant association between ART pregnancy and PP. Infertility etiology in ART patients increased risks of adverse pregnancy outcomes. ART singleton pregnancies in tubal disease, endometriosis, male infertility, and mixed infertility groups had significantly higher PP rates (aOR:2.70–9.33). No such association was found in the ovulation disorder group[ 24 ]. While endometriosis does not notably impact ART outcomes, excisional endometrioma surgeries negatively affect ovarian reserve[ 25 ]. ART and endometriosis together significantly raise maternal and perinatal morbidity, though some risks are due to infertility-related issues[ 26 ]. In women undergoing ART or with endometriosis, the frequency and amplitude of uterine contractions in the implantation period are enhanced. This may cause abnormal uterine peristalsis, resulting in embryo implantation near the cervix and lower placental implantation. Directly transferring the blastocyst into the uterine cavity via transcervical catheterization may disrupt normal placental process, increasing the risk of PP development and persistence[ 27 ]. In addition, this study compared maternal and neonatal outcomes in PP and general groups. Postpartum hemorrhage and preterm birth were higher in PP group, consistent with the results of previous studies[ 9 , 10 ]. This suggests PP negatively impacts both mother and neonate outcomes, increasing risks of labor complications. Limitations of this study include its retrospective nature and single-center design. It may not fully capture relevant clinical information, severity of endometriosis, treatments, and other medical conditions that affect obstetric outcomes. Despite this weakness, the strengths of this study include a large cohort of nulliparas individuals, and second, our hospital is a tertiary referral center offering advanced health care. Prior studies on PP's incidence and risk factors included nulliparas and multiparous subjects and mainly focused on risk factors for PP in women with childbirth history, like miscarriage, cesarean delivery. In addition, further studies are needed to understand how endometriosis history and severity of endometriosis affect placental migration. Conclusion In conclusion, histories of endometriosis, ART, and advanced maternal age are high-risk factors for PP in nulliparas. In addition, endometriosis history was significantly associated with PP in both ART and natural conceptions, posing an elevated risk for spontaneous pregnancies. Therefore, we should strengthen the promotion of reproductive health information, and pay close attention to patients with these risk factors in clinical practice, and take appropriate measures to improve the outcome of patients and newborns. Abbreviations PP Placenta previa ART Assisted reproductive techniques BMI Body mass index PPH Postpartum hemorrhage NICU Neonatal intensive care unit aOR Adjusted odds ratio CI Confidence interval Declarations Acknowledgments Not applicable. Author contributions Weiwei Cheng contributed to study conception and design. Xuemin Wei contributed to case collection, data analysis, and paper writing. Mi Xiang contributed to study design and data analysis. All authors were involved in drafting the manuscript or revising it. All authors read and agreed to the final version. Funding None Data availability statement The data that support the findings of this study are available from the corresponding author upon reasonable request. Conflict of interest The authors declare no competing interests. Ethics approval and consent to participate All procedures performed in studies involving human participants were approved by the local Ethics Committee of the International Peace Maternity and Child Health Hospital. Written informed consent was waived due to the retrospective study. Nevertheless, private information was well-protected during the study. Consent for publication Not applicable. References Jain V, Bos H, Bujold E, Guideline. 402: Diagnosis and Management of Placenta Previa. J Obstet Gynaecol Can. 2020;42(7):906–17. Naeem H, Fareeha H, Batool S, Naeem A, Waheed K, Saddozai M. 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Endometriosis and assisted reproductive techniques independently related to mother-child morbidities: a French longitudinal national study. Reprod Biomed Online. 2021;42(3):627–33. Galanti F, Riccio S, Giannini A, D'Oria O, Buzzaccarini G, Scudo M, et al. Placentation and complications of ART pregnancy. An update on the different possible etiopathogenic mechanisms involved in the development of obstetric complications. J Reprod Immunol. 2024;162:104191. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version 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-5339162","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":372038107,"identity":"32d9d9e9-4d49-4696-abf8-db767dd34a36","order_by":0,"name":"Xuemin Wei","email":"","orcid":"","institution":"the International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Xuemin","middleName":"","lastName":"Wei","suffix":""},{"id":372038108,"identity":"9f2828be-df52-496e-8510-cf5026118cd2","order_by":1,"name":"Mi Xiang","email":"","orcid":"","institution":"the International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Mi","middleName":"","lastName":"Xiang","suffix":""},{"id":372038109,"identity":"ad680938-f9d8-4bd8-9ee3-b7ebd42f7c65","order_by":2,"name":"Weiwei Cheng","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABAElEQVRIiWNgGAWjYFACxgYGBgMJZjb5xwcffADyDYjUYsHOz5CWbDgDpuUAYX0V/JINOWbSPMRoMTje3CbxoUBC2uDAAQNp2zYbeXMG3oOPP+DTcuZgm+QMAwljg4MNCca5bWmGOxv4kg3w2WJ2I7HtNo+BRLLBYYYDyblthxk3HOAxk8Cr5f7Dttt/DCTqNxxjbDhs2fbfHqjF/Ad+WxjbboMCWbKHmbGZse1AIsgWvN63P5PY/rMHqIVfgo2ZsedccvKGwzzGEmfwaJFsP/7Y4MefOmY2Cf7vP36U2dluON5j+KECjxZUwMgGJJiJVg4Gf0hTPgpGwSgYBSMDAAB9tVN+lWdOWwAAAABJRU5ErkJggg==","orcid":"","institution":"the International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Weiwei","middleName":"","lastName":"Cheng","suffix":""}],"badges":[],"createdAt":"2024-10-26 22:53:07","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5339162/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5339162/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":94672165,"identity":"00999f1d-c894-434e-89cd-a38775fd7182","added_by":"auto","created_at":"2025-10-29 13:39:37","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":817051,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5339162/v1/f5fe1e23-5d91-45f6-974b-d5a98c8d9ffd.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Risk Factors and Perinatal Outcomes for Placenta Praevia at Delivery in nulliparas: a Retrospective Case-control Study","fulltext":[{"header":"Background","content":"\u003cp\u003ePlacenta previa (PP) is the complete or partial covering of the internal os of the cervix with the placenta after the 28th week of gestation[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. In recent years, the occurrence of PP has gradually increased, which coincides with the rising rates of cesarean sections[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e], abortions[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e], and uterine surgical procedures[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. This trend translates to an estimated incidence of PP in approximately 1 out of every 200 to 250 live births[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. PP poses a significantly increased risk of dangerous complications, including obstetrical hemorrhage[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] and preterm birth[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. In severe cases, it can cause hemodynamic instability such as disseminated intravascular coagulation(DIC), necessitating immediate surgery, blood transfusion, or hysterectomy, potentially resulting in infertility, or even death[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe well-documented risk factors for PP are assisted reproductive techniques (ART) [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e], history of intrauterine surgeries[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e], and prior cesarean delivery[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. However, the exact etiology and pathogenesis of PP remain unclear so far. Additionally, there is a lack of sufficient research into risk factors for PP at delivery in nulliparas population. Therefore, this study aims to explore risk factors associated with PP at delivery in nulliparas pregnancy and to observe neonatal outcomes among affected individuals.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy setting and participants\u003c/h2\u003e \u003cp\u003eThis retrospective case-control study was conducted at the International Peace Maternity and Child Health Hospital (IPMCHH), a single tertiary referral medical center of Shanghai, east China, from January 1st, 2018 to December 31st, 2022. During this period, women delivered in our hospital had demographic and clinical data prospectively collected throughout pregnancy. Due to the retrospective nature of the study, patients were informed and signed informed consent forms at their first antenatal visit at IPMCHH, a teaching hospital for Shanghai JiaoTong University School of Medicine. This study was approved by the Ethics Committee of the International Peace Maternity and Child Health Hospital, in accordance with the Helsinki declaration.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eInclusion and exclusion criteria\u003c/h3\u003e\n\u003cp\u003eInclusion criteria: (1) 28 weeks\u0026thinsp;\u0026le;\u0026thinsp;pregnancy time\u0026thinsp;\u0026le;\u0026thinsp;41 weeks; (2) nulliparas with singleton pregnancy;(3) cesarean section to termination pregnancy; (4) complete case information; (5) meets the diagnostic criteria for PP.\u003c/p\u003e \u003cp\u003eExclusion criteria: (1) patients with previous history of cesarean section, or pregnancy; (2) women whose pregnancies were terminated or who delivered before 28 weeks; (3) no placenta previa at delivery; (4) twin pregnancy;(5) incomplete case information;(6) patients with hematologic disorders, malignant tumors, or infectious diseases.\u003c/p\u003e \u003cp\u003eFinally, a total of 464 nulliparas with singleton pregnancy complicated PP were grouped in the PP group. For each PP participant, 4 nulliparas without PP who gave birth on the same day were randomly selected as the control group (n\u0026thinsp;=\u0026thinsp;1856).\u003c/p\u003e\n\u003ch3\u003eClinical data collection\u003c/h3\u003e\n\u003cp\u003eData in the perinatal database is documented by attending physicians after delivery. Medical secretaries review the information before entry. Coding is done after evaluating prenatal care records and hospital documents. This ensures completeness and accuracy. The database includes demographic information, perinatal assessments, maternal morbidities, and newborns outcomes. Records are anonymized before analysis. The hospitalization database includes demographic information and International Classification of Diseases, ninth revision codes(ICD-9) for all diagnoses.\u003c/p\u003e \u003cp\u003eDemographic information includes maternal age, gestational week, history of endometriosis, ART, pregnancy comorbidities (chronic hypertension, pregestational diabetes, hypothyroidism), pre-pregnancy body mass index (BMI). Perinatal outcomes such as maternal related indicators (amount of postpartum bleeding, the rate of postpartum hemorrhage(PPH) and placenta adherence), and neonatal condition (birth week, birth weight, Apgar score at 5 min after birth) were also counted in both groups.\u003c/p\u003e \u003cp\u003eDiagnostic criteria for PP at delivery: placenta previa at delivery was identified when it was an indication for cesarean delivery in study participants. Placenta attached to the lower uterine segment reaching or covering the internal cervical os at delivery; also, intraoperative diagnosis based on the position of the placenta. Maternal age is defined as age in completed years at delivery. Advanced maternal age is defined as an age\u0026thinsp;\u0026ge;\u0026thinsp;35 years on the estimated date of delivery. BMI was calculated by using self-reported prepregnancy weight and height values (weight/height\u003csup\u003e2\u003c/sup\u003e, kg/m\u003csup\u003e2)\u003c/sup\u003e. Diagnosis of endometriosis was based on laparoscopy (gold standard), a history of surgical treatments such as cystectomy for ovarian endometriosis, ablation or excision of endometriotic implants, and adhesiolysis. PPH is defined as bleeding\u0026thinsp;\u0026ge;\u0026thinsp;1000 mL after delivery in 24 hours. ART includes: in vitro fertilization-embryo transfer (IVF), frozen embryo transfer and intracytoplasmic sperm injection(ICSI), but does not include intrauterine insemination from donor(IUI D), intrauterine insemination from spouse(IUI S) and other medically assisted reproduction: oocyte donation, fertility preservation, gestational carriers which are forbidden in China.\u003c/p\u003e\n\u003ch3\u003eStatistical Methods\u003c/h3\u003e\n\u003cp\u003eContinuous variables are expressed as the mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation and were evaluated using the t-test. Categorical variables are expressed as rates and were evaluated using the χ2 test, corrected χ2 test or Fisher\u0026rsquo;s exact test, as appropriate. Those data that did not meet normal distribution or equal variance were presented as median [M (P25, P75)], the Mann-Whitney U test was used for comparisons between two groups, and the Kruskal-Wallis rank sum test was used for comparisons between multiple independent samples. Univariate and multivariate logistic regression analyses were used to explore the risk factors of PP. Multivariate analysis was performed using binary logistic regression analysis. Stratified analysis was further analyzed to exclude confounders. To investigate ART's influence on the association between endometriosis and PP, we stratified the analysis by ART use. Missing data were not imputed.Statistical analysis was performed using SPSS 27.0 software (IBM Corp., Armonk, NY). All tests were two-sided, and p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered as statistically significant.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eDuring the study period, 68,310 women delivered at our hospital. Among them, 34,967 were nulliparas with singleton pregnancy, and 464 (0.68%) of these women were complicated with PP at delivery. Compared to the control group, the women in the PP group were older [32.72\u0026thinsp;\u0026plusmn;\u0026thinsp;4.04 vs 30.99\u0026thinsp;\u0026plusmn;\u0026thinsp;3.65, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001] and had significantly higher proportions of endometriosis history [16.2% vs 2.7%, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001], ART use [28.0% vs 10.1%, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001], intrauterine surgery history [9.5% vs 5.7%,P\u0026thinsp;=\u0026thinsp;0.003], and abortion surgery history [35.1% vs 29.3%, P\u0026thinsp;=\u0026thinsp;0.015] (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). There were no statistically significant differences between the two groups in terms of chronic hypertension, pregestational diabetes, hypothyroidism, pre-pregnancy BMI (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05,Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDemographics characteristics of placenta previa group and non-placenta previa group\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaternal characteristics\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePlacenta previa\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;464)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNon-Placenta previa\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;1856)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaternal age (y)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e32.72\u0026thinsp;\u0026plusmn;\u0026thinsp;4.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e30.99\u0026thinsp;\u0026plusmn;\u0026thinsp;3.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI category\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI\u0026thinsp;\u0026lt;\u0026thinsp;28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e453(97.6%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1776(95.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.054\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI\u0026thinsp;≧\u0026thinsp;28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11(2.4%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e80(4.3%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSmoker\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUse of ART\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYES\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e130(28.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e188(10.1%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e334(72.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1668(89.9%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHistory of endometriosis\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYES\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e75(16.2%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e51(2.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e389(83.8%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1804(97.3%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHistory of abortions\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYES\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e163(35.1%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e544(29.3%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.015\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e301(64.9%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1312(70.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHistory of hysteroscopic surgery\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYES\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e44(9.5%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e106(5.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.003\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e419(90.5%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1750(94.3%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eChronic hypertension\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYES\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e14(3.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e44(2.4%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.425\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e450(97.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1812(97.6%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePregestational diabetes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYES\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e19(4.1%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e50(2.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.112\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e445(95.9%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1806(97.3%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHypothyroidism\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYES\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e58(12.5%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e191(10.3%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.169\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e406(87.5%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1665(89.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eMaternal age is defined as age in completed years at delivery.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eBMI, pre-pregnancy body mass index was calculated by using self-reported prepregnancy weight and height values (weight/height\u003csup\u003e2\u003c/sup\u003e, kg/m\u003csup\u003e2\u003c/sup\u003e ).\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eSmoker: Smoked tobacco before pregnancy or during pregnancy.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eART, Assisted reproduction technology includes: In vitro fertilization-embryo transfer (IVF), frozen embryo transfer and Intracytoplasmic sperm injection(ICSI), but does not include Intrauterine insemination from donor(IUI D), Intrauterine insemination from spouse(IUI S) and other medically assisted reproduction: Oocyte donation, fertility preservation, gestational carriers which are forbidden in China.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eAdjusted odds ratios of risk factors for PP are described in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The presence or absence of PP was used as the dependent variable, and the indicators that differed in the univariate analysis, such as maternal age, history of endometriosis, ART, history of intrauterine surgery, history of abortion surgery were used as independent variables into a multifactorial logistic regression model. The results showed that advanced maternal age (aOR,1.81, 95%CI,1.40\u0026ndash;2.33), history of endometriosis (aOR, 5.50, 95% CI, 3.73\u0026ndash;8.10) and application of ART (aOR, 2.70, 95% CI,2.02\u0026ndash;3.61) were independent risk factors for PP at delivery (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05, Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eAdjusted odds ratios of factors associated with placenta previa\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003eUnivariate analysis\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eMultivariate logistic regression\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIndicators\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eOR(95% CI)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eaOR(95% CI)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaternal age\u0026thinsp;\u0026ge;\u0026thinsp;35(y)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.46(1.95\u0026ndash;3.10)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.81(1.40\u0026ndash;2.33)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI\u0026thinsp;\u0026ge;\u0026thinsp;28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.54(0.29\u0026ndash;1.02)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.048\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.53(0.27\u0026ndash;1.02)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.057\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eART\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.45(2.68\u0026ndash;4.45)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.70(2.02\u0026ndash;3.61)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHistory of endometriosis\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6.82(4.70\u0026ndash;9.89)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5.50(3.73\u0026ndash;8.10)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHistory of abortions\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.31(1.05\u0026ndash;1.62)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.015\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.21(0.97\u0026ndash;1.52)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.099\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHistory of hysteroscopic surgery\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.73(1.20\u0026ndash;2.50)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.83(0.54\u0026ndash;1.27)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.396\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eChronic hypertension\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.28(0.69\u0026ndash;2.36)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.426\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePregestational diabetes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.54(0.90\u0026ndash;2.64)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.115\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHypothyroidism\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.25(0.91\u0026ndash;1.70)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.170\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eOR: Odds Ratio; aOR: adjusted Odds Ratio;\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eMaternal age is defined as age in completed years at delivery.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eBMI, pre-pregnancy body mass index was calculated by using self-reported prepregnancy weight and height values (weight/height\u003csup\u003e2\u003c/sup\u003e, kg/m\u003csup\u003e2\u003c/sup\u003e ).\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eART, Assisted reproduction technology includes: In vitro fertilization-embryo transfer (IVF), frozen embryo transfer and Intracytoplasmic sperm injection(ICSI), but does not include Intrauterine insemination from donor(IUI D), Intrauterine insemination from spouse(IUI S) and other medically assisted reproduction: Oocyte donation, fertility preservation, gestational carriers which are forbidden in China.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eTables\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3.1\u003c/span\u003e and 3.2 outline the risk factors for developing PP by stratified analysis by ART use. Using stepwise model selection in multifactorial logistic regression model, the following 2 factors remained statistically significant in ART subgroup: advanced maternal age (aOR, 1.66; 95% CI, 1.03\u0026ndash;2.66), history of endometriosis (aOR, 2.25; 95% CI,1.15\u0026ndash;4.42) (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05, Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3.1\u003c/span\u003e). Similarly, the following 3 factors remained statistically significant in natural conception subgroup: advanced maternal age (aOR, 1.84; 95%CI,1.36\u0026ndash;2.48), history of endometriosis (aOR,7.69; 95%CI,4.85\u0026ndash;12.18) and history of abortion (aOR,1.36; 95%CI,1.05\u0026ndash;1.76)(P\u0026thinsp;\u0026lt;\u0026thinsp;0.05, Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e3.2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3.1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eStratified analysis by ART, univariate analysis for PP in ART subgroup ( n\u0026thinsp;=\u0026thinsp;318) and natural conception subgroup (n\u0026thinsp;=\u0026thinsp;2002)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003eART subgroup\u003c/p\u003e \u003cp\u003e( n\u0026thinsp;=\u0026thinsp;318)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eNatural conception subgroup (n\u0026thinsp;=\u0026thinsp;2002)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIndicators\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eOR (95% CI)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eOR (95% CI)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAdvanced maternal age\u0026thinsp;\u0026ge;\u0026thinsp;35(y)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.64(1.04\u0026ndash;2.57)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.032\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.08(1.56\u0026ndash;2.77)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI\u0026thinsp;\u0026ge;\u0026thinsp;28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.13(0.02\u0026ndash;0.98)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.058\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.72(0.37\u0026ndash;1.40)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.330\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHistory of endometriosis\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.52(1.30\u0026ndash;4.86)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8.26(5.24\u0026ndash;13.02)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHistory of abortions\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.74(0.45\u0026ndash;1.19)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.214\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.51(1.18\u0026ndash;1.93)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHistory of hysteroscopic surgery\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.79(0.48\u0026ndash;1.33)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.384\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.18(0.62\u0026ndash;2.24)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.609\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eChronic hypertension\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.57(0.17\u0026ndash;1.84)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.344\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.48(0.73\u0026ndash;3.03)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.280\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePre-gestational diabetes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.51(0.89\u0026ndash;13.83)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.073\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.29(0.67\u0026ndash;2.45)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.446\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ehypothyroidism\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.36(0.70\u0026ndash;2.65)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.364\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.17(0.81\u0026ndash;1.69)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.418\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3.2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMultivariate logistic regression for PP in ART subgroup ( n\u0026thinsp;=\u0026thinsp;318) and natural conception subgroup (n\u0026thinsp;=\u0026thinsp;2002)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003eART subgroup\u003c/p\u003e \u003cp\u003e( n\u0026thinsp;=\u0026thinsp;318)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eNatural conception subgroup (n\u0026thinsp;=\u0026thinsp;2002)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIndicators\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eaOR (95% CI)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eaOR (95% CI)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAdvanced maternal age\u0026thinsp;\u0026ge;\u0026thinsp;35(y)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.66(1.03\u0026ndash;2.66)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.036\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.84(1.36\u0026ndash;2.48)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHistory of endometriosis\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.25(1.15\u0026ndash;4.42)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7.69(4.85\u0026ndash;12.18)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHistory of abortions\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.36(1.05\u0026ndash;1.76)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.020\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eOR: Odds Ratio; aOR: adjusted Odds Ratio;\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eAdvanced maternal age is defined as age\u0026thinsp;\u0026ge;\u0026thinsp;35 years in completed years at delivery.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eBMI was calculated by using self-reported prepregnancy weight and height values (weight/height\u003csup\u003e2\u003c/sup\u003e, kg/m\u003csup\u003e2\u003c/sup\u003e ).\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eART, Assisted reproduction technology includes: In vitro fertilization-embryo transfer (IVF), frozen embryo transfer and Intracytoplasmic sperm injection(ICSI), but does not include Intrauterine insemination from donor(IUI D), Intrauterine insemination from spouse(IUI S) and other medically assisted reproduction: Oocyte donation, fertility preservation, gestational carriers which are forbidden in China.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e4\u003c/span\u003e describes pregnancy outcomes of placenta previa group and non-placenta previa group. Those with PP at delivery were more likely to have decreased gestational age at delivery (median, 37 weeks [32\u0026ndash;40] vs 39 weeks [29\u0026ndash;41];P\u0026thinsp;\u0026lt;\u0026thinsp;.0001), higher rate of preterm delivery at \u0026lt;\u0026thinsp;37 weeks\u0026rsquo; gestation (24.78% vs 5.82%;P\u0026thinsp;\u0026lt;\u0026thinsp;.0001), more intraoperative bleeding volume (424.58\u0026thinsp;\u0026plusmn;\u0026thinsp;343.64 vs 224.41\u0026thinsp;\u0026plusmn;\u0026thinsp;82.32;P\u0026thinsp;\u0026lt;\u0026thinsp;.0001), more placenta adherence (22.63% vs 4.74%;P\u0026thinsp;\u0026lt;\u0026thinsp;.0001) and lower neonatal birthweight (3025.26\u0026thinsp;\u0026plusmn;\u0026thinsp;439.08 vs 3307.03\u0026thinsp;\u0026plusmn;\u0026thinsp;492.49; P\u0026thinsp;=\u0026thinsp;0.01,Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e4\u003c/span\u003e). There were no differences in the following outcomes: stillbirth, NICU admission, 5-minute Apgar score\u0026thinsp;\u0026lt;\u0026thinsp;7, neonatal sex, and maternal or neonatal death (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05,Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePregnancy outcomes of placenta previa group and Non-placenta previa group\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePregnancy outcomes\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePlacenta previa\u003c/p\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;464\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNon-placenta previa\u003c/p\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;1856\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eMaternal outcomes\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGestational age (weeks)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e37(32\u0026ndash;40)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e39(29\u0026ndash;41)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.031\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreterm delivery (\u0026lt;\u0026thinsp;37 week)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e115(24.78%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e108(5.82%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIntraoperative bleeding volume(ml)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e424.58\u0026thinsp;\u0026plusmn;\u0026thinsp;343.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e224.41\u0026thinsp;\u0026plusmn;\u0026thinsp;82.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePPH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e30(6.47%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4(0.22%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePlacenta adherence\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e105(22.63%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e88(4.74%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaternal death\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eFetal/Neonatal outcomes\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStillbirth\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026gt;\u0026thinsp;0.99\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNeonatal birthweight (g)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3025.26\u0026thinsp;\u0026plusmn;\u0026thinsp;439.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3307.03\u0026thinsp;\u0026plusmn;\u0026thinsp;492.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.012\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLow Neonatal birthweight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e47(10.13%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e98(5.28%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNeonatal Sex\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e235(50.65%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1016(54.74%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.113\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e229(49.35%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e840(45.26%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5-min Apgar\u0026thinsp;\u0026lt;\u0026thinsp;7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8(1.72%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e27(1.45%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.670\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNICU admission\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6(1.30%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22(1.20%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.849\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNeonatal death\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003ePreterm delivery :Defined as birth before completed weeks of gestation.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003ePPH: Postpartum hemorrhage, defined as \u0026ge;\u0026thinsp;1000 mL during the 24 h after delivery.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003ePlacenta adherence:Pathological adhesion or implantation of placenta, unable to be naturally peeled off, requiring manual peeling.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eLow Neonatal birthweight :defined as a neonate whose birth weight\u0026thinsp;\u0026lt;\u0026thinsp;2500g.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eNICU admission : Admission to neonatal intensive care unit from the delivery room or maternity ward.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this study, PP incidence was 0.68% in nulliparas at delivery. Compared to the control group, PP patients were older and had higher rates of endometriosis, ART use, intrauterine surgery, and abortion. After adjusting analysis by multivariate logistic regression, the 3 statistically significant risk factors for PP at delivery were endometriosis, ART use, and advanced maternal age. Stratified analysis showed endometriosis linked to PP in both ART group and natural conceptions, especially raising spontaneous pregnancy risk. Additionally, nulliparas with PP faced higher risks of preterm birth, hemorrhage and placenta adherence, but no significant differences in stillbirth, NICU admission, Apgar scores, or neonatal/maternal death.\u003c/p\u003e \u003cp\u003eThis study showed endometriosis history was an independent risk factor for PP in nulliparas, those with endometriosis history had 5.50 times higher risk than those without. Meta-analysis revealed that endometriosis showed higher risk of PP, with odds ratio of 3.03\u0026ndash;3.31[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], and preterm delivery[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Endometriosis history remains a risk factor for PP even after adjusting for other parameters[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e], maternal age, ART, multiplicity, and previous deliveries did not alter these differences[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. This aligns with our study's key findings. Moreover, Farella M et al[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] reported that independent factors associated with PP include conception via ART and a history of stage III or IV endometriosis. Women with deep endometriosis have a higher risk of PP[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAdditionally, in this study, stratified analysis showed that endometriosis history was significantly associated with PP in both ART and natural conceptions subgroup, posing an elevated risk for spontaneous pregnancies. Similarly, previous studies[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] found endometriosis raised PP risk, independent of medically assisted reproduction, with a slight risk increase in spontaneous pregnancies. Compared to non-endometriosis women with non-ART pregnancies, PP risk was higher in both endometriosis women with or without ART [No endo/ART (aRR 2.26, 99% CI 1.42\u0026ndash;3.60), Endo/no ART (aRR 1.66, 99% CI 1.18\u0026ndash;2.33)][\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Our study focused on nulliparas women, excluding cesarean history, is congruent with these findings. These results indicate endometriosis women, including ART users, need heightened pregnancy surveillance and management. However, the pathogenesis of PP remains unclear. Reasons may include pelvic adhesions, abnormal uterine position, limited uterine mobility, or abnormal uterine contractions, causing placenta displacement. Endometriosis can alter endometrial properties and affect placental implantation. Adequate progesterone levels regulate the endometrium, and endometriosis can induce progesterone resistance, leading to PP[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Therefore, the exact pathogenesis of PP needs further research to clarify.\u003c/p\u003e \u003cp\u003eOur study found that nulliparas conceiving via ART had increased risk of PP at delivery. Previous study[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] similarly observed a significant association between ART pregnancy and PP. Infertility etiology in ART patients increased risks of adverse pregnancy outcomes. ART singleton pregnancies in tubal disease, endometriosis, male infertility, and mixed infertility groups had significantly higher PP rates (aOR:2.70\u0026ndash;9.33). No such association was found in the ovulation disorder group[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. While endometriosis does not notably impact ART outcomes, excisional endometrioma surgeries negatively affect ovarian reserve[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. ART and endometriosis together significantly raise maternal and perinatal morbidity, though some risks are due to infertility-related issues[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. In women undergoing ART or with endometriosis, the frequency and amplitude of uterine contractions in the implantation period are enhanced. This may cause abnormal uterine peristalsis, resulting in embryo implantation near the cervix and lower placental implantation. Directly transferring the blastocyst into the uterine cavity via transcervical catheterization may disrupt normal placental process, increasing the risk of PP development and persistence[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn addition, this study compared maternal and neonatal outcomes in PP and general groups. Postpartum hemorrhage and preterm birth were higher in PP group, consistent with the results of previous studies[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. This suggests PP negatively impacts both mother and neonate outcomes, increasing risks of labor complications.\u003c/p\u003e \u003cp\u003eLimitations of this study include its retrospective nature and single-center design. It may not fully capture relevant clinical information, severity of endometriosis, treatments, and other medical conditions that affect obstetric outcomes. Despite this weakness, the strengths of this study include a large cohort of nulliparas individuals, and second, our hospital is a tertiary referral center offering advanced health care. Prior studies on PP's incidence and risk factors included nulliparas and multiparous subjects and mainly focused on risk factors for PP in women with childbirth history, like miscarriage, cesarean delivery. In addition, further studies are needed to understand how endometriosis history and severity of endometriosis affect placental migration.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn conclusion, histories of endometriosis, ART, and advanced maternal age are high-risk factors for PP in nulliparas. In addition, endometriosis history was significantly associated with PP in both ART and natural conceptions, posing an elevated risk for spontaneous pregnancies. Therefore, we should strengthen the promotion of reproductive health information, and pay close attention to patients with these risk factors in clinical practice, and take appropriate measures to improve the outcome of patients and newborns.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003ePP \u0026nbsp; \u0026nbsp; \u0026nbsp; Placenta previa\u003c/p\u003e\n\u003cp\u003eART \u0026nbsp; \u0026nbsp; \u0026nbsp;Assisted reproductive techniques\u003c/p\u003e\n\u003cp\u003eBMI \u0026nbsp; \u0026nbsp; \u0026nbsp;Body mass index\u003c/p\u003e\n\u003cp\u003ePPH \u0026nbsp; \u0026nbsp; Postpartum hemorrhage\u003c/p\u003e\n\u003cp\u003eNICU \u0026nbsp; Neonatal intensive care unit\u003c/p\u003e\n\u003cp\u003eaOR \u0026nbsp; \u0026nbsp; Adjusted odds ratio\u003c/p\u003e\n\u003cp\u003eCI \u0026nbsp; \u0026nbsp; \u0026nbsp; Confidence interval\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWeiwei Cheng contributed to study conception and design. Xuemin Wei contributed to case collection, data analysis, and paper writing. Mi Xiang contributed to study design and data analysis. All authors were involved in drafting the manuscript or revising it. All authors read and agreed to the final version.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data that support the findings of this study are available from the corresponding author upon reasonable request.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll procedures performed in studies involving human participants were approved by the local Ethics Committee of the International Peace Maternity and Child Health Hospital. Written\u0026nbsp;\u003c/p\u003e\n\u003cp\u003einformed consent was waived due to the retrospective study. Nevertheless, private information was well-protected during the study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eJain V, Bos H, Bujold E, Guideline. 402: Diagnosis and Management of Placenta Previa. J Obstet Gynaecol Can. 2020;42(7):906\u0026ndash;17.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNaeem H, Fareeha H, Batool S, Naeem A, Waheed K, Saddozai M. Frequency of Placenta Previa in Women with Prior Caesarean Section and Its Relation with Increasing Number of Caesarean Sections and Maternal Factors. Gomal J Med Sci. 2024;22(1):76\u0026ndash;80.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSun H, Mao J, Su X, Du Q. Impact of spontaneous abortion history and induced abortion history on perinatal outcomes of singleton pregnancies. BMC Public Health. 2023;23(1).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKing LJ, Dhanya Mackeen A, Nordberg C, Paglia MJ. Maternal risk factors associated with persistent placenta previa. Placenta. 2020;99:189\u0026ndash;92.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJansen CHJR, Kastelein AW, Kleinrouweler CE, Van Leeuwen E, De Jong KH, Pajkrt E, et al. Development of placental abnormalities in location and anatomy. Acta Obstet Gynecol Scand. 2020;99(8):983\u0026ndash;93.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAbecassis A, Wainstock T, Sheiner E, Miodownik S, Pariente G. Risk factors for early postpartum hemorrhage: A retrospective, population-based, cohort analysis. Int J Gynaecol Obstet. 2024;166(2):812\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJansen CHJR, van Dijk CE, Kleinrouweler CE, Holzscherer JJ, Smits AC, Limpens JCEJM, et al. Risk of preterm birth for placenta previa or low-lying placenta and possible preventive interventions: A systematic review and meta-analysis. Front Endocrinol (Lausanne). 2022;13:921220.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHan X, Guo Z, Yang X, Yang H, Ma J. Association of Placenta Previa With Severe Maternal Morbidity Among Patients With Placenta Accreta Spectrum Disorder. JAMA Netw Open. 2022;5(8):e2228002.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSahu SA, Shrivastava D. Maternal and Perinatal Outcomes in Placenta Previa: A Comprehensive Review of Evidence. Cureus. 2024;16(5):e59737.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKumari U, Naniwal A, Rani V, Chandat R, Yadav S, Pipal DK. A Study of Clinical Characteristics, Demographic Characteristics, and Fetomaternal Outcomes in Cases of Placenta Previa: An Experience of a Tertiary Care Center. Cureus. 2022;10.7759/cureus.32125.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKarami M, Jenabi E, Fereidooni B. The association of placenta previa and assisted reproductive techniques: a meta-analysis. J Matern Fetal Neonatal Med. 2018;31(14):1940\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJenabi E, Salimi Z, Bashirian S, Khazaei S, Ayubi E. The risk factors associated with placenta previa: An umbrella review. Placenta. 2022;117:21\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZullo F, Spagnolo E, Saccone G, Miriam A, Serena X, Marcello C, et al. Endometriosis and obstetrics complications: a systematic review and meta-analysis. Fertil Steril. 2017;108(4):667\u0026ndash;e6725.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLalani S, Choudhry AJ, Firth B, Bacal V, Walker M, Wen SW, et al. Endometriosis and adverse maternal, fetal and neonatal outcomes, a systematic review and meta-analysis. Hum Reprod. 2018;33(10):1854\u0026ndash;65.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVendittelli F, Barasinski C, Rivi\u0026egrave;re O, Bourdel N, Fritel X. Endometriosis and risk of adverse pregnancy outcomes: a retrospective multicenter cohort study. Fertil Steril Published online July. 2024;30. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.fertnstert.2024.07.037\u003c/span\u003e\u003cspan address=\"10.1016/j.fertnstert.2024.07.037\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKato K, Iriyama T, Hara K, Suzuki K, Hashimoto A, Sayama S, et al. Increased risk of placenta previa and preterm birth in pregnant women with endometriosis/adenomyosis: A propensity-score matching analysis of a nationwide perinatal database in Japan. J Obstet Gynaecol Res. 2024;50(3):351\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eG\u0026oacute;mez-Pereira E, Burgos J, Mendoza R, P\u0026eacute;rez-Ruiz I, Olaso F, Garc\u0026iacute;a D, et al. Endometriosis Increases the Risk of Placenta Previa in Both IVF Pregnancies and the General Obstetric Population. Reprod Sci. 2023;30(3):854\u0026ndash;64.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFarella M, Chanavaz-Lacheray I, Verspick E, Merlot B, Klapczynski C, Hennetier C, et al. Pregnancy outcomes in women with history of surgery for endometriosis. Fertil Steril. 2020;113(5):996\u0026ndash;1004.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eUccella S, Manzoni P, Cromi A, Marconi N, Gisone B, Miraglia A, et al. Pregnancy after Endometriosis: Maternal and Neonatal Outcomes according to the Location of the Disease. Am J Perinatol. 2019;36(S 02):S91\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGebremedhin AT, Mitter VR, Duko B, Tessema GA, Pereira GF. Associations between endometriosis and adverse pregnancy and perinatal outcomes: a population-based cohort study. Arch Gynecol Obstet. 2024;309(4):1323\u0026ndash;31.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVelez MP, Bougie O, Bahta L, Pudwell J, Griffiths R, Li W, et al. Mode of conception in patients with endometriosis and adverse pregnancy outcomes: a population-based cohort study. Fertil Steril. 2022;118(6):1090\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eIbiebele I, Nippita T, Baber R, Torvaldsen S. Pregnancy outcomes in women with endometriosis and/or ART use: a population-based cohort study. Hum Reprod. 2022;37(10):2350\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePost RJ, Chang J, Ziogas A, Crosland BA, Silver RM, Haas DM, et al. Risk factors and perinatal outcomes for persistent placenta previa in nulliparas. Am J Obstet Gynecol MFM. 2023;5(10):101136.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang J, Liu Q, Deng B, Chen F, Liu X, Cheng J. Pregnancy outcomes of Chinese women undergoing IVF with embryonic cryopreservation as compared to natural conception. BMC Pregnancy Childbirth. 2021;21(1):39.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSomigliana E, Li Piani L, Paffoni A, Salmeri N, Orsi M, Benaglia L, et al. Endometriosis and IVF treatment outcomes: unpacking the process. Reprod Biol Endocrinol. 2023;21(1):107.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEpelboin S, Labrosse J, Fauque P, Levy R, Gervoise-Boyer MJ, Devaux A, et al. Endometriosis and assisted reproductive techniques independently related to mother-child morbidities: a French longitudinal national study. Reprod Biomed Online. 2021;42(3):627\u0026ndash;33.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGalanti F, Riccio S, Giannini A, D'Oria O, Buzzaccarini G, Scudo M, et al. Placentation and complications of ART pregnancy. An update on the different possible etiopathogenic mechanisms involved in the development of obstetric complications. J Reprod Immunol. 2024;162:104191.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Placenta previa, Nulliparas pregnancy, History of endometriosis, Assisted reproductive techniques, Perinatal outcome, Risk factors","lastPublishedDoi":"10.21203/rs.3.rs-5339162/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5339162/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003ePlacenta previa leads to dangerous obstetrical outcomes, including obstetrical hemorrhage and preterm birth, and its rate is still increasing.The objective is to analyze the risk factors for placenta previa in nulliparas population, and to observe the perinatal outcomes of these patients.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eThis retrospective analysis was conducted at the International Peace Maternity and Child Health Hospital, China, from January 2018 to December 2022. The placenta previa group consisted of 464 nulliparas with placenta previa at delivery. For each placenta previa patients, 4 nulliparas without placenta previa who gave birth on the same day were randomly selected as the control group (n\u0026thinsp;=\u0026thinsp;1856). Multivariable logistic regression were employed for adjusted analyses to identify risk factors for placenta previa. Stratified analysis by assisted reproductive techniques(ART) was used to exclude confounders. Furthermore, maternal and neonatal outcomes were compared between the two groups.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eAmong 68,310 deliveries included in the analysis, 464 (0.68%) nulliparas with singleton pregnancy of these women had placenta previa at delivery. Histories of endometriosis [Adjusted Odds Ratio (aOR) 5.50], ART [aOR 2.70], and advanced maternal age [aOR 1.81] emerged as significant risk factors for placenta previa. Stratified analysis showed endometriosis linked to placenta previa both in ART [aOR 2.25] and natural conceptions [aOR 7.69], significantly raising spontaneous pregnancy risk. Notably, the placenta previa group exhibited a significantly higher proportion of maternal and neonatal adverse outcomes compared to the control group (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eIn nulliparas, endometriosis, ART, and advanced maternal age emerge as independent risk factors for placenta previa at delivery, leading to adverse perinatal outcomes. In addition, endometriosis history was significantly associated with placenta previa in ART and natural conceptions, increasing risk for spontaneous pregnancies.\u003c/p\u003e","manuscriptTitle":"Risk Factors and Perinatal Outcomes for Placenta Praevia at Delivery in nulliparas: a Retrospective Case-control Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-11-08 20:07:12","doi":"10.21203/rs.3.rs-5339162/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"6a4fa2f9-b7e2-4a7f-a83f-6296cdbe325f","owner":[],"postedDate":"November 8th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-10-29T08:54:08+00:00","versionOfRecord":[],"versionCreatedAt":"2024-11-08 20:07:12","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5339162","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5339162","identity":"rs-5339162","version":["v1"]},"buildId":"ehx78VzkSd0WSzXnipQa-","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}