Incidence of neonatal sixth nerve palsy in relation to mode of delivery.

During a 10-year period on a level I neonatal service the total incidence (0.4%) and incidence by mode of delivery of neonatal lateral rectus paralysis occurring among 6886 term neonates was determined. The incidence of abducens nerve injury in this population increased progressively from 0% for deliveries by cesarean section to 0.1% for spontaneous vaginal delivery, to 2.4% for forceps delivery, and to 3.2% for vacuum extraction. This suggests that increased complexity of instrumentation during delivery is associated with an increased risk of sixth nerve palsy. A proposed mechanism for the injury to the sixth nerve is described.