The association between epidural analgesia and perineal injury in primiparous women: A propensity score-matched cohort study.

Objective: To determine the association between epidural analgesia and perineal injury, including obstetric anal sphincter injury (OASI), in primiparous women.

Methods: We conducted a retrospective cohort study of primiparous women with singleton, term, vertex, and vaginal deliveries between 2012 and 2024 at a tertiary medical center. Primary outcomes were (1) any perineal injury, and (2) OASI. Propensity score matching (1:1) was used to adjust for maternal and obstetric confounders. Perineal outcomes were compared in matched and unmatched cohorts using standardized mean difference (SMD). An SMD <0.1 was considered negligible, 0.1-0.2 small, and >0.2 clinically significant. Multivariable logistic regression was used to evaluate associations between epidural use and outcomes.

Results: Overall, 45 132 women were included, of whom 36 799 (81.5%) received epidural analgesia. After matching (n = 5974 per group), baseline characteristics were balanced apart from fetal head station at full dilation, which was higher in the no-epidural group (0.90 ± 0.9 vs. 0.66 ± 0.8; SMD = 0.239). Perineal injury occurred more often with epidural with a marginal difference (82.2% vs. 78.2%, SMD = 0.10). In a multivariable logistic regression analysis, epidural was associated with more perineal injury only in the absence of episiotomy (adjusted odds ratio [aOR] 1.321; 95% confidence interval [CI]: 1.225-1.425; P < 0.001), but not when episiotomy was performed. Conversely, epidural use was associated with lower OASI risk regardless of whether episiotomy was performed (aOR 0.492; 95% CI: 0.285-0.849; P = 0.011) or not (aOR 0.592; 95% CI: 0.424-0.825; P = 0.002).

Conclusion: In primiparous term vaginal deliveries, epidural analgesia modestly increased low-grade perineal tears but reduced OASI risk, supporting its safety regarding severe perineal trauma.