OBJECTIVE: Neurological injury associated with present day labor and delivery is thought to be unusual. The purpose of this study was to estimate the incidence, severity, and duration of postpartum lumbosacral spine and lower extremity nerve injury and identify factors related to nerve injury. METHODS: All women who delivered a live-born infant from July 1997 through June 1998 were asked about symptoms of lumbosacral spine and lower extremity nerve injury the day after delivery. Women with symptoms were examined by a physiatrist to confirm injury, and their cases were then followed by telephone until the symptoms resolved. Maternal variables (including prospective documentation of time spent pushing in various positions) and fetal variables that might be associated with risk of nerve injury were compared between women with injury and those without. RESULTS: Six thousand fifty-seven women delivered live-born infants; 6048 were interviewed and 56 had a confirmed new nerve injury, an incidence of 0.92%. Factors found by logistic regression analysis to be associated with nerve injury were nulliparity and prolonged second stage of labor. Women with nerve injury spent more time pushing in the semi-Fowler-lithotomy position than women without injury. The median duration of symptoms was 2 months. CONCLUSION: The estimated incidence of postpartum nerve injury was greater than reported from previous studies and is associated with nulliparity and prolonged second stage of labor.