Objectives To quantify, firstly, temporal trends in episiotomy use among spontaneous vaginal deliveries (SVDs) and operative vaginal deliveries (OVDs) in Canada, and secondly, the associations between episiotomy and obstetric anal sphincter injury (OASI) among SVDs and OVDs. Methods Population-based, retrospective, cohort study of all singleton, term deliveries in Canada (2004-2014) using hospitalization data. Temporal trends in episiotomy use by parity, previous cesarean delivery and mode of delivery were tested using the Cochran-Armitage test. Logistic regression was used to estimate the association between episiotomy and OASI among women with SVD and OVD after controlling for confounders. Results The study included 1,442,484 deliveries. Among nulliparous women, there was a smaller absolute decline in episiotomy use among SVDs (22.9% in 2004 to 14.1% in 2014; p<0.0001) than OVDs (59.3% to 49.9%; p<0.0001). Although episiotomy use was less frequent in parous women without a previous cesarean, temporal trends in episiotomy rates were similar to those in nulliparous women. Among nulliparous women with an SVD, episiotomy was associated with higher rates of OASI (5.8% with episiotomy vs 4.6% without; AOR 1.25, 95% CI 1.21-1.29). In contrast, episiotomy was associated with lower rates of OASI among women with an OVD (15.3% vs 16.7%; AOR 0.90, 95% CI 0.88-0.93) and this association was strongest among forceps deliveries (17.8% vs 27.2%; AOR 0.63, 95% CI 0.60-0.67). Conclusions Episiotomy use has declined in Canada in recent years among SVDs and OVDs. There is a pressing need to consider episiotomy use in OVD (especially with forceps) given the protective association between episiotomy and OASI.
