van Bavel J, et al. - This retrospective population-based cohort study was planned to assess whether mediolateral episiotomy is associated with a reduction in the rate of obstetric anal sphincter injuries (OASIS) during operative vaginal delivery. Findings revealed that in primiparous and multiparous women, a fivefold to tenfold reduction in the rate of OASIS was evident in association with the use of a mediolateral episiotomy during both vacuum delivery and forceps delivery.