Hospital-based lateral episiotomy and obstetric anal sphincter injury rates: a retrospective population-based register study

ObjectiveWe sought to determine whether an optimal level of lateral episiotomy use can be found by assessing the correlation between the hospital-based variations in episiotomy use and rates/odds ratios of obstetric anal sphincter injuries (OASIS).Study DesignThis was a retrospective population-based register study. The study group, comprising women with spontaneous singleton vaginal deliveries, contained all 154,175 primiparous and all 234,236 multiparous women. The correlations between lateral episiotomy use and incidence/risk of OASIS (n = 1659) were assessed using nonlinear and linear regression modeling.ResultsThe rates of episiotomy were inversely correlated with the risk of OASIS among both groups of women. OASIS rates increased from 0.5-1.0% as episiotomy rates decreased from 80-40%.ConclusionRestricting lateral episiotomy use may result in higher OASIS rates. However, we could not determine the optimal level of episiotomy use since individual hospitals deviated substantially from the correlation curves.