Are sphincter defects the cause of anal incontinence after vaginal delivery? Results of a prospective study.

PURPOSE: Anal incontinence affects approximately 10 percent of adult females. Damage to the anal sphincters has been considered as the cause of anal incontinence after childbirth in the sole prospective study so far available. The aims of the present study were to determine prospectively the incidence of anal incontinence and anal sphincter damage after childbirth and their relationship with obstetric parameters.

METHODS: We studied 259 consecutive females six weeks before and eight weeks after delivery. They were asked to fill in a questionnaire assessing fecal incontinence. Anal endosonography (7-10 MHz) was then performed. Two independent observers analyzed internal and external anal sphincters.

RESULTS: A total of 233 patients (90 percent) were assessed, of whom 31 had cesarean section. De novo sphincter defects were observed in 16.7 percent (14 percent external, 1.7 percent internal, and 1 percent both) in the postpartum period only after vaginal delivery. These disruptions occurred with the same incidence after the first and the second childbirth. Independent risk factors (odds ratio; 95 percent confidence interval) for sphincter defect were forceps (12; 4-20), perineal tears (16; 9-25), episiotomy (6.6; 5-17), and parity (8.8; 4-19) as revealed by multivariate analyses. The overall rate of anal incontinence was 9 percent and independent risk factors (odds ratio; 95 percent confidence interval) involved forceps (4.5; 1.5-13), perineal tears (3.9; 1.4-10.9), sphincter defect (5.5; 5-15), and prolonged labor (3.4; 1-11). Among these patients only 45 percent had sphincter defects.

CONCLUSION: Anal incontinence after delivery is multifactorial, and anal sphincter defects account for only 45 percent of them. Primiparous and secundiparous patients have the same risk factors for sphincter disruption and anal incontinence. Because external anal sphincter disruptions are more frequent than internal anal sphincter damage, surgical repair should be discussed in symptomatic patients.