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

BACKGROUND

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).

OBJECTIVE

To evaluate whether there is increased prevalence of OASI in VBAC compared with primiparous women.

SEARCH STRATEGY: Literature search using PubMed, Embase and Cochrane databases.

SELECTION CRITERIA: 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.

DATA COLLECTION AND ANALYSIS: This systematic review included 23 articles conducted in 11 countries over 19 years. Included studies were analysed using RevMan version 5.4.

MAIN

RESULTS

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%).

CONCLUSION

Women undergoing VBAC had a higher prevalence of OASI compared with primiparous women.