Episiotomy and the risk of obstetric anal sphincter injury in nulliparous women with a prolonged second stage

Abstract Purpose This study aimed to evaluate whether episiotomy reduces obstetric anal sphincter injuries (OASIS) rates in nulliparous women with a second stage of labor lasting ≥ 3 h. Methods This retrospective study focused on nulliparous women at ≥ 36 weeks of gestation with singleton pregnancies who experienced a second stage of labor lasting ≥ 3 h and ultimately achieved spontaneous, non-operative, vaginal delivery between 2014 and 2024. Participants were categorized into two groups based on their episiotomy status. The primary outcome was the occurrence of OASIS, namely third- and fourth-degree perineal lacerations. Results The study included 1164 (58.3%) women who underwent episiotomy and 831 (41.7%) who did not. Women in the episiotomy group were significantly younger (27.79 ± 4.31 vs. 28.47 ± 4.51 years, p < 0.001), had a higher prevalence of hypertensive disorders (7.7% vs. 5.2%, p = 0.029), experienced a slightly longer second stage of labor (3.62 ± 0.4 vs. 3.53 ± 0.4 h, p < 0.001), and delivered newborns with higher birthweight (3366 ± 390 vs. 3284 ± 376 g, p < 0.001). The OASIS rates were comparable between the groups (1.9% vs. 2.2%, p = 0.82), consistent across all subtypes and in a subanalysis of women with a second stage of ≥ 4 h (2.9% vs. 2.5%, p = 0.59). In adjusted multivariable analysis, episiotomy was not associated with OASIS (adjusted OR 0.95, 95% CI 0.48–1.84). Conclusion In nulliparous women with spontaneous vaginal delivery and a prolonged second stage (≥ 3 h), episiotomy was not associated with a reduced risk of OASIS, even when the second stage exceeded 4 h. Our findings support existing guidelines that advocate against routine episiotomy in this population.