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

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.