Obstetric brachial plexus palsy: A birth injury not explained by the known risk factors

Objective. To determine the incidence and prognosis of obstetric brachial plexus injuries and analyze associated risk factors. Design. Analysis of prospectively collected information comprising all births from 1991 to 2000, with complete follow-up of affected children. Setting. St Olav's University Hospital, a tertiary care hospital in the middle part of Norway. Population. Thirty thousand five hundred and seventy-four children; all were examined within 24 hours of birth and 91 were diagnosed with brachial plexus injury. Methods. We reviewed the hospital records and analyzed the data submitted from our hospital to the Medical Birth Register of Norway. Result. Risk factors are shoulder dystocia, macrosomy, diabetes, vacuum extraction and forceps delivery. The predictive power of these variables is poor. Almost half of the plexus injuries followed spontaneous vaginal deliveries with second stage of 30 minutes or less. Two newborns were delivered by cesarean section and two were vaginal breech deliveries. In 15 children (0.5/1,000) a permanent plexus injury has been diagnosed. Compared with transient plexus impairment, risk factors for a permanent injury were high maternal body mass index, shoulder dystocia, fractured humerus and fetal asphyxia. Fracture of the clavicle was significantly more frequent when the injury was transient, possibly reflecting a protective effect. Conclusion. The incidence of obstetric brachial plexus injury is 0.3% and the recovery rate is 84%, resulting in 0.5 permanent injuries per 1,000 births. Plexus injury is not well predicted by known risk factors. Other etiological factors should be sought.