Injury to innervation of pelvic floor sphincter musculature in childbirth.

71 women delivered at St Bartholomew's Hospital, London, were studied by electrophysiological tests of the innervation of the external anal sphincter muscle and by manometry. The investigations were done 2-3 days after delivery and again, in 70% of these women, 2 months later. Faecal and urinary incontinence developing after vaginal delivery has been thought to be due to direct sphincter division, or muscle stretching, but the results of the study suggest that in most cases this incontinence results from damage to the innervation of the pelvic floor muscles.