Risk Factors, Prognosis and Prediction Models for Placenta Accreta Without Prior Cesarean Section：A Prospective Cohort Study

The placenta accreta spectrum (PAS) is defined as abnormal placental trophoblast adherence with a wide range of myometrial invasion. It is a serious pregnancy complication that can lead to severe postpartum hemorrhage, which may necessitate hysterectomy, and could ultimately lead to maternal death.Previous studies have shown that women with the highest risk of PAS disorders are those with a prior cesarean section (CS) who present in the second trimester of pregnancy with any degree of placenta previa or low-lying placenta.PAS patients without prior CS represent about one-third of the entire PAS population.The strategy to identify at-risk patients without a prior CS has yet to be defined. This may lead to under identification of PAS patients without prior CS and create a missed opportunity to plan the delivery and improve prognosis in these women. Established risk factors distinct from prior CS delivery include in vitro fertilization (IVF), intrauterine implants, endometritis, uterine artery embolization manual placental removal, uterine malformation, adenomyosis, submucosal fibroids, smoking, maternal weight, maternal age, parity, and multifetal pregnancy. Large clinical studies focusing on PAS disorders in women without prior CS are, indeed, scarce.This study aims to explore the risk factors and prognosis of PAS without a history of cesarean section and try to establish the prediction model.