Obstetric anal sphincter injury and anal incontinence following vaginal birth: a systematic review and meta-analysis.

Introduction: The aim of this study was to systematically review current evidence for the relationship between obstetric anal sphincter injury (ie, episiotomy and third- or fourth-degree perineal lacerations) and anal incontinence in parous women.

Methods: PubMed, Ovid (MEDLINE), Cochrane Trials, and Cumulative Index to Nursing and Allied Health Literature were searched. Studies eligible for review assessed the relationship between episiotomy and/or third- or fourth-degree perineal laceration and anal incontinence. Two reviewers independently searched for studies for review and used the Meta-Analysis of Observational Studies in Epidemiology guidelines. Quality of individual studies was appraised using the Downs and Black criteria. Pooled effect sizes were estimated for the relationships between episiotomy and third- or fourth-degree perineal laceration with anal incontinence using random effects meta-analysis models. Heterogeneity of each model was assessed using Cochran Q and I(2) statistics.

Results: Of 578 articles, 19 studies (7 prospective cohort studies, 6 retrospective studies, one case-control study, and 5 population-based cross-sectional studies) met inclusion/exclusion criteria for the systematic review. Of the 19 studies, 3 examined episiotomy, 7 examined third- or fourth-degree perineal laceration, and 9 studies examined both risk factors for anal incontinence. Eight studies (N = 2929 women) examining the relationship between episiotomy and anal incontinence and 12 studies (N = 2288 women) examining the relationship between third- or fourth-degree perineal laceration and anal incontinence met criteria for inclusion in the meta-analyses. Pooled odds ratios (ORs) demonstrated a significant association between perineal trauma (episiotomy [OR, 1.74; 95% confidence interval [CI], 1.28-2.38; Q = 8.9; P < .26; I(2) = 21.4] and third- or fourth-degree perineal laceration (OR, 2.66; 95% CI, 1.77-3.98; Q = 27.9; P = .002; I2 = 64.1) and anal incontinence.

Discussion: Both episiotomy and third- or fourth-degree perineal laceration are significantly associated with anal incontinence after vaginal birth. The evidence provided in this systematic review and meta-analysis highlights the importance of reducing perineal trauma during vaginal births in order to ameliorate anal incontinence in parous women.