Shoulder dystocia is an uncommon but serious complication of delivery. Clinically, shoulder dystocia may be diagnosed when delivery of the head is followed by an inability to deliver the shoulders. Shoulder dystocia generally requires additional maneuvers to free the shoulders and effect delivery of the infant. Although the exact mechanism is not well studied, the postulated mechanism is impaction of the anterior shoulder against the maternal symphysis pubis or impaction of the posterior shoulder on the sacrum. Rarely, dystocia may be the result of or may be made worse by impaction against the soft tissue of the birth canal.