Prolonged second stage of labor and risk of postpartum hemorrhage in nullipara with epidural anesthesia and vaginal delivery: A cohort study with propensity score analysis.

Objective: To conduct an analysis using propensity score methods, exploring the association between a prolonged second stage (>3 h) and the risk of postpartum hemorrhage (PPH) in a diverse population.

Methods: We conducted a prospective cohort study involving nullipara with epidural anesthesia and vaginal delivery, aged ≥18 years, presenting cephalically, and with a gestational age (GA) of ≥24 weeks at a tertiary maternity hospital in China (chictr.org.cn identifier: ChiCTR2200063094). Women undergoing emergency cesarean section in labor were excluded. The primary outcome was PPH, with secondary outcomes including severe postpartum hemorrhage and blood transfusion. We employed propensity score overlap weighting to analyze the association between prolonged second stage labor and PPH.

Results: The study included 3643 nullipara with epidural anesthesia, comprising 77 with a second stage of labor >3 h and 3566 with a second stage ≤3 h. Utilizing propensity score overlap weighting, there were no significant differences observed between the two groups regarding the risk of PPH (29.87% in >3 h group vs 17.64% in ≤3 h group; weighted odds ratio 1.01; 95% CI: 0.51-2.02). Subgroup interaction tests for PPH were not significant for assisted vaginal delivery, induction of labor, macrosomia, third-/fourth-degree perineal laceration, GA >41 weeks, twin pregnancies, episiotomy and GA >37 weeks. Sensitivity analysis did not reveal significant differences.

Conclusion: This study did not find evidence supporting an increased risk of PPH associated with a second stage of labor lasting >3 h in our population, providing additional evidence for clinical practice.