Objective: The use of episiotomy during operative vaginal birth (OVB) is rather debated among operators and in literature. It is also important to evaluate the indications for which episiotomy is performed. In fact, the consequences of an episiotomy can be invalidating for patients with long-lasting results. The aim of this study is the evaluation of the role of episiotomy during OVB with the vacuum extractor and its correlation with Obstetric Anal Sphincter Injuries (OASIs).Methods: On of 9165 vaginal births, a total of 498 OVB (5.4%) were enrolled in a longitudinal prospective observational study. The incidence of OASIs was evaluated in our population after OVB performed with the vacuum extractor, during which the execution of episiotomy was performed indicated by clinician in charge.Results: OASIs occurred in 4% of the patients (n = 20). Episiotomy was performed in 39% of them (n = 181). OASIs incidence was 6% (n = 17) in the No Episiotomy and 1.8% (n = 3) in Episiotomy group (p<.001). Performance of episiotomy during OVB determined a protective effect against OASIs (p = 0.025 in full cohort and p = 0.013 in the primiparous group). An expulsive phase under one hour was an almost significant protective factor (p = 0.052).Conclusions: The use of episiotomy during OVB was associated with much lower OASIs rates in nulliparous women with a vacuum extraction; OR 0.23 (CI 95% 0.07-0.81) p = 0.037 in nulliparous women and the number necessary to treat was 18 among nulliparous women to prevent 1 OASIs. A further risk factor that emerged from the analysis is a prolonged expulsive period, whereas fundal pressure does not seem to have a statistically significant influence.
Keywords: OASIs; Operative vaginal birth; episiotomy; obstetric anal sphincter injuries; perineal tear.