Mediolateral Episiotomy Reduces the Risk for Anal Sphincter Injury During Operative Vaginal Delivery

Abstract

Injury to the anal sphincter during childbirth is accepted as a major risk factor for fecal incontinence in women. As many as 50% of women with such injury report fecal incontinence, due mainly to a persistently defective sphincter. Risk factors for anal sphincter injury during operative vaginal delivery were examined in a population-based observational study of 7478 Dutch women who had forceps delivery and 21,254 who delivered by vacuum extraction. Cases were taken from a validated Dutch national obstetrical database for the years 1994–1995. Partial sphincter injuries were included. Anal sphincter injury occurred in 646 women delivered with vacuum extraction (3.0%) and in 348 of those who had forceps delivery (4.7%). Risk factors for anal sphincter injury during delivery aided by vacuum extraction included primiparity, higher fetal birth weight, an occipitoposterior position, and the duration of the second stage of labor. Induction of labor did not appear to alter the risk. Mediolateral episiotomy during vacuum extraction had a highly protective effect, lowering the risk of a third-degree perineal tear by nearly 90% (odds ratio [OR], 0.11; 95% confidence interval [CI], 0.09–0.13). The number of mediolateral episiotomies needed to prevent 1 anal sphincter injury after vacuum-assisted delivery was 12.4. Significant risk factors for anal sphincter damage in forceps deliveries included primiparity, occipitoposterior position, and higher fetal birth weight. The duration of second-stage labor was not a significant risk factor. As with vacuum extraction, induced labor carried no added risk. Mediolateral episiotomy correlated with a considerable reduction in the risk of anal sphincter damage (OR, 0.09; 95% CI, 0.07–0.11). The number of episiotomies needed to prevent a single sphincter injury during forceps delivery was 5.0 (95% CI, 4.4–5.7). The investigators conclude that mediolateral episiotomy should be routinely performed during operative vaginal deliveries in order to avoid injuring the anal sphincter.