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Clinical Obstetrics

Poster Session 1

(118) Mediolateral Episiotomy and Obstetric Anal Sphincter Injuries in Nullipara: A Propensity Score Matching Study

Tuesday, February 13, 2024
10:30 AM – 12:00 PM  
Location: Prince George's Exhibit Hall CDE, Lower Atrium Level
Objective: The potential protective effect of mediolateral episiotomy against obstetric anal sphincter injuries (OASIs) is controversial. We aimed to investigate mediolateral episiotomy's role in preventing OASIs during vaginal deliveries (VD) or vacuum-assisted deliveries (VAD).

Study Design: Retrospective observational study at a tertiary center, from August 2007 to September 2019. Inclusion criteria were for all nulliparous women with a singleton gestation who underwent VD or VAD at ≥ 37 gestational weeks. To adjust for confounding, propensity score matching with a 1:1 ratio was employed. The primary outcome was the incidence of OASIs, and the secondary outcome was a composite of immediate neonatal outcomes (umbilical artery pH < 7.1, neonatal intensive care unit admission, and 5-minute Apgar score < 7).

Results: The study cohort comprised 22,787 deliveries: 17,546 VD (77%) and 5,241 VAD (23%). Episiotomy rates were 38.5% and 75.9% in VD and VAD, respectively. After matching, both groups showed good balance in body mass index, post-term pregnancy, oxytocin use, neuraxial anesthesia, and birth weights. Separate analyses were conducted for the matched VD group (n = 13,500) and the matched VAD group (n = 2,518). Episiotomy was associated with a lower risk of grade 1 and 2 tears in VD (OR 0.110, 95% CI 0.100 – 0.121) and VAD (OR 0.472, 95% CI 0.378 – 0.590). Regarding OASIs, no significant differences were observed in VD (OR 1.147, 95% CI 0.779-1.688) or VAD (OR 0.581, 95% CI 0.324-1.039). However, in VAD, episiotomy demonstrated a borderline protective effect against OASIs with a number needed to treat = 104.917 (95% CI 42.640 - 167.194). Conversely, episiotomy in NVD was associated with a higher rate of composite neonatal outcome (OR 1.227, 95% CI 1.036-1.453), while VAD showed no such association (OR 1.115, 95% CI 0.871-1.426).

Conclusion: Propensity score matching reveals no significant protective effect of mediolateral episiotomy on OASIs in women undergoing VD. However, there is a possible benefit in VAD.