Incidence and Predictors of Anal Incontinence After Obstetric Anal Sphincter Injury in Primiparous Women

Abstract

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).

Figure 1. Consort Diagram of Participant Status

* The 12 and 24 week calls were not included in the original RCT design. Participants who consented to the study under the original protocol were only followed beyond 6 weeks if their consent allowed for further contact.