Is episiotomy worthwile to prevent obstetric anal sphincter injury during operative vaginal delivery in nulliparous women?

Abstract

Objectives: Episiotomy is a marker of Obstetric Anal Sphincter Injury (OASIS) condition, therefore, unmeasured factors could have biased the strength of the association between episiotomy and reduced OASIS during Operative Vaginal Delivery (OVD). The aim of this study was to compare the OASIS rate during OVD according to episiotomy practice.

Study design: Retrospective cohort study of all nulliparous pregnant women attempting an OVD between 2014-2017. To avoid unmeasured bias, all maternal and delivery data were prospectively captured after the birth. The strong relationship between parity and episiotomy practice (indication bias) lead to analyze only nulliparous women. Association between mediolateral episiotomy and OASIS following OVD was performing by using multivariate logistic regression analysis including significant variable in univariate analysis and relevant factors known to be associated both with OASIS and/or OVD.

Results: Over the study period, 1709 (17.1%) women had an OVD, among them 40 (2.3%) had OASIS. In the 1342 (78.5%) nulliparous women, OASIS rate were 2% and 5.1% with and without episiotomy (p < 0.01). In multivariate analysis a lower incidence of OASIS with the use of episiotomy (OR 0.267 IC 0.132-0.541) were observed. The persistent occiput posterior position was associated with an increase risk of OASIS (OR 6.742 IC 2.376-19.124). Spatula/forceps, as compared to vacuum operative vaginal delivery increased the risk OASIS (OR 2.847 IC 1.311-7.168). Area under the curve of the model was 0.745.

Conclusion: Episiotomy is a modifiable risk factors which can contribute to reduce the risk of OASIS in nulliparous women with operative vaginal delivery. This intervention should be included in a global management of the second stage of labor.

Keywords: Episiotomy; Nulliparous; Obstetric anal sphincter injury; Occiput posterior; Operative vaginal delivery.