A systematic review of the efficacy of cesarean section in the preservation of anal continence

Purpose: Elective primary cesarean section is performed largely to avoid maternal pelvic trauma that may result in anal incontinence, although its efficacy in this regard has not been thoroughly assessed. We perform a systematic review of published reports that compare anal incontinence risk by mode of delivery. Methods: PubMed was searched from 1966 through August 2005. Authors were contacted for missing data or analyses. Both randomized and nonrandomized reports were included. Eligible studies included females having vaginal delivery or cesarean section, fecal and/or flatal incontinence was reported as an outcome, and risk was calculable from the reported data. Crude data were extracted from the reports, as well as reported odds ratios and confidence intervals. In the nonrandomized studies, adjusted odds ratios also were extracted and additional data obtained from authors to adjust risks for age and parity if not originally done. Sensitivity analyses were performed using quality indicators: age and parity adjustment, time to continence assessment. and mode of previous delivery. Results: Fifteen studies were found eligible, encompassing 3,010 cesarean sections and 11,440 vaginal deliveries. The summary relative risk for fecal incontinence was 0.91 (95 percent confidence interval, 0.74-1.14). For flatus the relative risk was 0.98 (range, 0.86-1-13). The number needed to treat by cesarean section was 167 to prevent a single case of fecal incontinence. Five studies were judged to be of high quality. In these studies, the summary relative risk was 0.94 (range, 0.72-1.22) and number needed to treat was 198. Conclusions: The best evidence to assess the efficacy of cesarean section in the prevention of anal incontinence would be in randomized trials of average-risk pregnancies with few crossovers. In the absence of such trials and based on this review, cesarean section does not prevent anal incontinence. This implies that incontinence associated with delivery may be more likely incontinence caused by pregnancy.