Incidence and predictors of anal incontinence after obstetric anal sphincter injury in primiparous women

Objective This study aimed to describe the incidence of fecal incontinence (FI) at 6, 12, and 24 weeks postpartum; anal incontinence (AI) and fecal urgency at 24 weeks; and identify predictors of AI in women with obstetric anal sphincter injury (OASI). Methods Primiparous women sustaining OASIs were identified at 8 clinical sites. Third-degree OASIs were characterized using World Health Organization criteria, 3a (<50%) or 3b (>50%) tear through the sphincter. Fecal incontinence was defined as leakage of liquid/solid stool and/or mucus in the past month; AI was defined as leakage of liquid/solid stool and/or mucus and/or gas in the past month and was assessed at 6, 12, and 24 weeks postpartum using the Fecal Incontinence Severity Index. Logistic regression identified variables associated with AI. Results Three hundred forty-three women participated: 297 subjects sustained a third-degree OASI, 168 type 3a, 98 type 3b and 31 indeterminant; 45 had a fourth-degree OASI. Overall FI incidence at 6, 12, and 24 weeks was 7% [23/326; 95% confidence interval (CI), 4%-10%], 4% (6/145; 95% CI, 2%-9%), and 9% (13/138; 95% CI, 5%-16%), respectively. At 24 weeks, AI incidence was 24% (95% CI, 17%-32%) and fecal urgency 21% (95% CI, 15%-29%). No significant differences in FI and AI rates were noted by third-degree type or between groups with third and fourth OASI. Flatal incontinence was greater in women sustaining a fourth-degree tear (35% vs 16%, P = 0.04). White race (adjusted odds ratio, 4.64; 95% CI, 1.35-16.02) and shorter duration of second stage (adjusted odds ratio, 1.47 per 30 minute decrease; 95% CI, 1.12-1.92) were associated with AI at 24 weeks. Conclusions Overall 24-week incidence of FI is 9% (95% CI, 5%-16%) and AI is 24% (95% CI, 17%-32%). In women with OASI, white race and shorter second-stage labor were associated with postpartum AI. Clinical Trial Registration: NCT01166399 (http://clinicaltrials.gov)