Hehir MP, et al. - In women with shoulder dystocia, risk factors for obstetric anal sphincter injury were investigated. Researchers analyzed a retrospective cohort of 685 women with shoulder dystocia and identified the risk of anal sphincter injury of 9%. Nulliparity, operative vaginal delivery, and use of internal maneuvers were the risk factors, however, episiotomy was observed to have a protective effect against anal sphincter injury during cases of shoulder dystocia.

Methods

• Researchers performed a retrospective analysis including all cases of shoulder dystocia from 2007 to 2011 at two large tertiary referral centers, in the USA and Ireland.
• In cases of shoulder dystocia, they analyzed details of maternal demographics, intrapartum characteristics, and delivery outcomes.
• They used univariate and multivariate analyses to delineate the association between shoulder dystocia and anal sphincter injury.

Results

• Researchers identified 685 cases of shoulder dystocia; the rate of shoulder dystocia was similar at both institutions.
• They noticed anal sphincter injury incidence of 8.8% (60 out of 685).
• In nulliparas, the rate was 14% (45 out of 324) and in multiparas, 4.2% (15 out of 361).
• Women with sphincter injury were more frequently nulliparous (75% [45 out of 60] vs 45% [279 out of 625]; p < 0.0001), have had an operative vaginal delivery (50% [30 out of 60] vs 36% [226 out of 625]; p = 0.03) and required internal maneuvers (50% [30 out of 60] vs 32% [198 out of 625], p = 0.004) than those with an intact sphincter.
• Multivariate regression analysis revealed that these predictors of sphincter injury remained significant when adjusted for other risk factors.
• They recognized a negative association of episiotomy with sphincter injury on multivariate regression analysis.