Characteristics, Complications and Perinatal Outcomes in Placenta Previa Women: a Prospective, Matched Case-control Study

Placenta previa (PP) is defined as the placenta overlying the endocervical os and grades according to the relationship and the distance between the lower placental edge and the internal os of the uterine cervix: low-lying previa, marginal previa, partial previa, and complete previa.

Cesarean delivery and assisted reproductive technology are associated with an increased risk of placenta previa in subsequent pregnancies. Other risk factors for previa include previous spontaneous, elective pregnancy terminations, previous uterine surgery, increasing maternal age and maternal parity, multiple gestations, smoking, cocaine use, and prior previa.

It is associated with numerous adverse maternal and fetal-neonatal complications, such as perinatal hemorrhage, preterm birth, blood transfusion, hysterectomy, maternal intensive care unit admission, disseminated intravascular coagulation, septicemia, thrombophlebitis, and even fetal-neonatal and maternal death.

This is a 1:2 prospective, matched and hospital-based case-control study to investigate the characteristics, complications and perinatal outcomes in pregnant women with placenta previa. For each placenta previa women, the investigators selected two none-placenta previa pregnant women as control from the same department matched on the mode of delivery, using simple random selection when excess matches are available. The date of their admission is limited to two days.

This hospital is a tertiary university-affiliated medical center with a stable number of approximately 12,000 deliveries per year. Placenta previa is diagnosed by experienced ultrasonologists based on a transabdominal ultrasonic finding of placental tissue covering the internal cervical os before delivery, and further confirmed by obstetricians at delivery.