Impact of liberal use of mediolateral episiotomy on the incidence of obstetric anal sphincter tear

To assess the impact of liberal compared with restrictive use of mediolateral episiotomy on the incidence of obstetric anal sphincter tear (OAST). Data between the years 1999-2001 (era 1) when liberal mediolateral episiotomy was applied were compared with the years 2004-2008 (era 2) when restricted mediolateral episiotomy was implemented. Liberal mediolateral episiotomy was done for fetal or maternal indications, while restrictive mediolateral episiotomy was done when a tear was imminent. Primary outcome was the incidence of OAST. A total of 25,170 women who delivered vaginally were included. After adjusting for potential confounders, the incidence of OAST was found to be significantly higher in era 2 (0.4 %) compared to era 1 (0.1 %), (p = 0.02; adjusted OR 2.23; 95 % CI, 1.16-4.29). Among primiparous women, the incidence of mediolateral episiotomy was 71.8 and 27.1 % in eras 1 and 2, respectively (p < 0.001), and the incidence of OAST was 0.2 and 1 % in eras 1 and 2, respectively (p = 0.009; adjusted OR 4.15; 95 % CI, 1.42-12.10). Among multiparous women, the incidence of OAST did not differ significantly (p = 0.52). Returning to the liberal policy among primiparous women only, 124 deliveries are needed to prevent one OAST. Liberal compared to restrictive use of mediolateral episiotomy may be a sphincter-saving procedure among primiparous women.