Impact of Episiotomy During Operative Vaginal Delivery on Obstetrical Anal Sphincter Injuries.

Abstract

The purpose of this study was to describe associations between episiotomy at the time of forceps or vacuum-assisted delivery and obstetrical anal sphincter injuries (OASIS). This population-based retrospective cohort study used delivery information from a provincial perinatal clinical database. Full-term, singleton, in-hospital, operative vaginal deliveries of vertex-presenting infants from April 1, 2006 to March 31, 2016 were identified. Odds ratios (ORs) and 95% confidence intervals (CIs) for associations between episiotomy and third- or fourth-degree lacerations were calculated in multiple logistic regression models (Canadian Task Force Classification II-2). Episiotomy was performed in 34% of 52241 operative vaginal deliveries. OASIS occurred in 21% of forceps deliveries and 7.6% of vacuum deliveries. Episiotomy was associated with increased odds of severe perineal lacerations for vacuum deliveries among women with (OR 2.48; 95% CI 1.96-3.13) and without (OR 1.12; 95% CI 1.02-1.22) a prior vaginal delivery. Among forceps deliveries, episiotomy was associated with increased odds of OASIS for those with a previous vaginal delivery (OR 1.52; 95% CI 1.12-2.06), but it was protective for women with no previous vaginal delivery (OR 0.73; 95% CI 0.67-0.79). Midline compared with mediolateral episiotomy increased the odds of OASIS in forceps deliveries (OR 2.73; 95% CI 2.37-3.13) and vacuum deliveries (OR 1.94; 95% CI 1.65-2.28). In conclusion, results suggest that episiotomy should be used with caution, particularly among women with a previous vaginal delivery and in the setting of vacuum-assisted delivery. Episiotomy may protect against OASIS in forceps-assisted deliveries for women without a prior vaginal delivery.