Increased risk of obstetric anal sphincter injury in women undergoing vaginal delivery after caesarean section: A systematic review and meta-analysis.

Abstract

There is increased focus on obstetric anal sphincter injury (OASI) and there are several well-established risk factors such as birthweight, instrumental delivery and median episiotomy. Some studies have found increased risk of OASI in women delivering vaginally after a previous caesarean section (VBAC). To evaluate whether there is increased prevalence of OASI in VBAC compared with primiparous women. Literature search using PubMed, Embase and Cochrane databases. All studies with data on both primiparous women and women undergoing VBAC were included. All included studies were evaluated using the "SIGN - methodology checklist" to verify if the quality was acceptable. This systematic review included 23 articles conducted in 11 countries over 19 years. Included studies were analysed using RevMan version 5.4. We found increased prevalence of OASI in the VBAC group; 8.18% (95% confidence interval [CI] 8.07-8.29) compared with 6.59% (95% CI 6.56-6.62) in primiparous women. Correspondingly, the meta-analysis revealed increased prevalence for OASI in the VBAC group (odds ratio 1.27, 95% CI 1.10-1.47). We found a high level of heterogeneity (I²  = 98%). Women undergoing VBAC had a higher prevalence of OASI compared with primiparous women.