[What are the risk factors of anal incontinence after vaginal delivery?].

Fecal incontinence is one of the most feared complications of vaginal delivery. It may be the consequence of sphincter tears, of pudendal neuropathy, or of a combination of the two. Fecal incontinence occurs immediately following 13-54% of vaginal deliveries but its persistence in the mid and long term is poorly known. The incidence of perineal tear with anal sphincteric defect varies from 1-9% and the incidence of unrecognized sphincter injury may be as high as 18-35%. Half the women who undergo primary anal sphincter repair have short or long term continence problems. Pudendal neuropathy is caused by nerve stretch during pushing in the second stage of labor and descent of the fetal head; it may occur even with the first delivery. Risk factors for sphincter injury and pudendal neuropathy include forceps delivery, large neonatal size, and prolonged second stage of labor. The risk of fecal incontinence must be considered even during the first pregnancy. Routine episiotomy does not prevent sphincter injury and may even predispose to it. Pudendal neuropathy following delivery may lead to delayed fecal incontinence abetted by postmenopausal hormonal deficiency and tissue senescence. The possible benefit of early episiotomy for women at high risk of sphincter injury must be evaluated by prospective studies.