Effect of second vaginal delivery on anorectal physiology and faecal continence: a prospective study

Background Because obstetric injury to the anal sphincters may be occult, a nd because the mechanism of injury differs between first and subsequent del iveries, we prospectively assessed the effects of first and second vaginal deliveries on anal physiology and continence. Methods We undertook a prospective observational study of 59 previously nul liparous women through two successive vaginal deliveries by means of a bowe r-function questionnaire, and an anorectal-physiology assessment, both ante partum and 6-12 weeks post parium. Findings 13 (22%) women reported altered faecal continence after their firs t vaginal delivery: eight had persistent symptoms during their second pregn ancy, of whom seven deteriorated after the second delivery; five regained c ontinence before their second pregnancy, but two became incontinent again a fter the second delivery. Five women developed incontinence for the first t ime after their second vaginal delivery, of whom three had occult primiparo us sphincter injury. 20 (34%) women, seven of whom had no symptoms, had ana l-sphincter injury as a result of their first delivery, but only two new in juries occurred after the second vaginal delivery (p=0.013). Although puden dal neuropathy was no more common after the second than after the first vag inal delivery (15 vs 19%, p=0.8), pudendal-nerve latency was longer after t he second delivery (p=0.02). Interpretation Primiparous women with persistent symptoms of altered faecal continence experience deterioration after a second vaginal delivery. Women with transient faecal incontinence or occult anal-sphincter injury after t heir first vaginal delivery are at high risk of faecal incontinence after a second vaginal delivery. The risk of mechanical anal sphincter injury is g reatest after the first delivery.