Can Obstetric Anal Sphincter Injury Be Predicted and Prevented?
B – Where episiotomy is indicated, the mediolateral technique is recommended, with careful attention to the angle cut away from the midline. Risk factors for third-degree tears have been identified in a number of retrospective studies. Taking an overall risk of 1% of vaginal deliveries, the following factors are associated with an increased risk of a third-degree tear: • Birth weight over 4 kg (up to 2%) • Persistent occipitoposterior position (up to 3%) • Nulliparity (up to 4%) • Induction of labour (up to 2%) • Epidural analgesia (up to 2%) • Second stage longer than 1 hour (up to 4%) • Shoulder dystocia (up to 4%) • Midline episiotomy (up to 3%) • Forceps delivery (up to 7%) Classification and Terminology How Should Obstetric Anal Sphincter Injury Be Classified? C – It is recommended that the classification outlined in this guideline be used when describing any obstetric anal sphincter injury. The following classification, described by Sultan*, has been adopted by the International
