Impact of mediolateral episiotomy on incidence of obstetrical anal sphincter injury diagnosed by endoanal ultrasound

Abstract Objective to examine potential association between mediolateral episiotomy and reduced incidence of obstetrical anal sphincter injuries (OASIS) diagnosed by endoanal ultrasound. Design prospective cohort study. Setting tertiary referral university hospital. Participants sixty nulliparous women at 28–33 weeks of gestation with singleton pregnancies were included between 2010 and 2012. Measurements and findings participants were examined with endoanal ultrasound at 28–33 weeks gestation and at 6–7 weeks post-partum. At both visits, symptoms of anal incontinence were assessed using Cleveland Clinic (Wexner) faecal incontinence scoring system. Mann Whitney U -test and χ 2 test was used to compare groups with vs. without episiotomy and groups with vs. without OASIS diagnosed by ultrasound. χ 2 test was used to assess correlation between OASIS and anal incontinence symptoms ( p ≤0.05 considered significant). None of the women included had sphincter injury or anal incontinence before childbirth. All delivered vaginally. Mediolateral episiotomy was performed in 33 (55%) cases. Six (10%) had OASIS on endoanal ultrasound (two were also diagnosed clinically), and 11 had symptoms of anal incontinence post-partum. No significant differences were seen in clinical characteristics between groups with vs. without episiotomy. No significant differences were seen in episiotomy rate ( p =0.14), angle ( p =0.42) and length ( p =0.14) between groups with vs. without OASIS on ultrasound. Correlation between anal incontinence symptoms and sonographically diagnosed OASIS was statistically significant ( p =0.04). Key conclusions mediolateral episiotomy does not seem to be protective against clinically or sonographically diagnosed OASIS even when episiotomy technique is considered. Endoanal ultrasound allows a significantly better detection of symptomatic OASIS compared to clinical examination alone. Implications for practice mediolateral episiotomy should be considered only when shortening the second stage of labour is indicated due to foetal distress, and not as a means of OASIS prevention.