Obstetric anal sphincter injury: how to avoid, how to repair: a literature review.

Avoiding obstetrical injury to the anal sphincter is the single biggest factor in preventing anal incontinence among women. Any form of instrument delivery has consistently been noted to increase the risk of obstetric anal sphincter injury and altered fecal continence by between 2- and 7-fold. Routine episiotomy is not recommended. Episiotomy use should be restricted to situations where it directly facilitates an urgent delivery. A mediolateral incision, instead of a midline, should be considered for persons at otherwise high risk of obstetric anal sphincter injury. The internal anal sphincter needs to be separately repaired if torn. Women with injuries to the internal anal sphincter or rectal mucosa have a worse prognosis for future continence problems. All women, particularly those with risk factors for injury, should be surveyed for symptoms of anal incontinence at postpartum follow-up.