Audit of the relationship between episiotomy and risk of major perineal laceration during childbirth.

The beneficial effect of mediolateral episiotomy in reducing major perineal lacerations during childbirth has been questioned. In a test of the hypothesis of no association between episiotomy and the incidence of major perineal lacerations, the incidence of major perineal laceration was determined in three cohort groups in one maternity unit between 1984 and 1991. Among those undergoing non-instrumental delivery, no reduction in the incidence of major lacerations could be demonstrated following episiotomy. Among those undergoing episiotomy, the incidence of major lacerations was significantly higher following instrumental delivery.