Risk of postpartum hemorrhage according to the planned mode of delivery among pregnant women with one previous cesarean delivery: a secondary analysis of the lower uterine segment trial.

Abstract

Postpartum hemorrhage is the most common complication in obstetrics and is a leading cause of serious maternal morbidity. Women with one previous cesarean delivery are at risk for postpartum hemorrhage. The aim of this study was to compare the risk of postpartum hemorrhage according to the planned mode of delivery among women with one previous cesarean delivery. This study was a secondary analysis of the Lower Uterine Segment Trial. The primary outcome was postpartum hemorrhage, and the secondary outcome was a composite of severe postpartum hemorrhage including the need for blood transfusion, second-line therapy to stop bleeding, or hysterectomy. The exposure was the planned mode of delivery, which was decided at around 36 weeks of gestation. Multivariate logistic regression analysis with a random intercept of the maternity unit was used to assess the relationship between the planned mode of delivery and postpartum hemorrhage. A secondary analysis using inverse probability weighting was performed to limit indication bias. Of the 2948 women included in the Lower Uterine Segment Trial, 2889 women were included in this secondary analysis; 2689 (93.0%) chose planned vaginal delivery, and 200 (7.0%) planned cesarean delivery. The rate of postpartum hemorrhage was lower in the planned cesarean delivery group than in the planned vaginal delivery group (2.5% vs 7.5%, adjusted odds ratio 0.28 [0.11-0.69] P<.01). The rate of the composite maternal outcome of severe postpartum hemorrhage was similar between the 2 groups (2.9% vs 2.0%, adjusted odds ratio 0.66 [0.24-1.83] P=.42). These results were consistent in the secondary analysis involving inverse probability weighting (odds ratio 0.35 [0.24-0.51] P<.01). Planned cesarean delivery was associated with a lower percentage of women with postpartum hemorrhage compared with planned vaginal delivery after one previous cesarean delivery. However, the use of transfusion, second-line therapies, or hysterectomy was rare, and the rates were similar between the 2 groups.