Does anal sphincter injury preclude subsequent vaginal delivery?

Abstract

ObjectiveTo assess continence and anal sphincter integrity during a subsequent pregnancy and delivery in women known to have a previous anal sphincter injury. DesignProspective observational study. SettingThe National Maternity Hospital, Dublin, Ireland. PopulationAntenatal patients with a documented obstetric anal sphincter injury at a previous delivery. MethodsWomen underwent symptom scoring, endoanal ultrasound and manometry. Main outcome measuresRecommended and actual mode of delivery, continence scores and endoanal ultrasound findings after index delivery. Results557 women were studied. 293 (53%) had no symptoms of faecal incontinence, 189 (34%) had mild symptoms and 75 (13%) moderate or severe symptoms.408 (73%) had an endoanal ultrasound. 383(94%) had a normal or small (<1 quadrant) defect in the internal anal sphincter and 390 (96%) had a scar or small (<1e quadrant) defect in the external anal sphincter.393 (70%) delivered vaginally. 164 (30%) were delivered by caesarean section. 197/557 (35%) returned for follow-up. There was no significant change in continence following either vaginal or caesarean delivery. 20 (5.1%) women had a recognised second anal sphincter tear during vaginal delivery. ConclusionsThe majority of women who sustain a third degree tear have minimal or no symptoms of faecal incontinence when assessed antenatally in a subsequent pregnancy. 70% go on to have a vaginal delivery, with little impact on faecal continence. These findings provide reassurance for patients and clinicians about the safety of vaginal delivery following anal sphincter injury in appropriately selected patients.