To evaluate the effect of the timing of previous cesarean section on outcomes of subsequent pregnancy complicated with placenta previa.

This was a retrospective cohort study. 658 women with placenta previa, who were all singleton pregnancies and had only one previous cesarean section, were analyzed in Third Affiliated Hospital of Guangzhou Medical University from October 2016 to October 2021. According to the timing of the previous cesarean section, the patients were divided into Elective cesarean (EC group) and Intrapartum cesarean (IC group). The two groups′ clinical characteristics and maternal and neonatal outcomes were analyzed.

There were 505 cases in the EC group and 153 cases in the IC group. No significant differences were found in age, BMI, abortion frequency, reproductive-assisted pregnancy rate and distance from the previous cesarean section between the two groups. The rates of placenta accrete spectrum disorders (69.9% vs 55.6%, χ²=10.858), intraoperative hemorrhage volume (<1000ml: 57.6% vs 75.8%, 1000~2000 ml: 31.7% vs 20.3%, >2000 ml: 10.7% vs 3.9%, χ²=17.466), blood transfusion volume (>0 but ≤400 ml: 10.1% vs 11.1%, >400 but ≤1200 ml: 15.4% vs 11.1%, >1200 ml: 12.3% vs 5.2%, χ²=9.083), the rates of ICU occupancy (3.2% vs 0), postoperative hospitalization days (5 vs 4, Ζ=-2.528), total hospitalization days (9 vs 8, Ζ=-2.260) and the term delivery rate (32.3% vs 45.1%, χ²=8.448) between the EC group and the IC group were statistically significant (P<0.05).

Elective caesarean section before labor onset is a high-risk factor for placenta previa complicated with PAS in a subsequent pregnancy, and maternal and neonatal adverse outcomes are higher.