The Epidemiology of Brachial Plexus Birth Palsy in the United States: Declining Incidence and Evolving Risk Factors

Background: The epidemiology of brachial plexus birth palsy (BPBP) in the United States may be changing over time due to population-level changes in obstetric care. Methods: The Kids' Inpatient Database from 1997 to 2012 was analyzed. Annual estimates of BPBP incidence and disease determinant distribution were calculated for the general population and the study population with BPBP. Long-term trends were analyzed. A multivariate logistic regression model was used to quantify the risk associated with each determinant. Results: The database yielded a combined total of 5,564,628 sample births extrapolated to 23,385,597 population births. The population incidence of BPBP dropped 47.1% over the 16-year study period, from 1.7 to 0.9 cases per 1000 live births (P<0.001). Female, black, and Hispanic subgroups had moderately increased risks of BPBP. Among children with BPBP, 55.0% had no identifiable risk factor. Shoulder dystocia was the strongest risk factor for BPBP in the regression model [odds ratio (OR), 113.2; P<0.001], although the risk of sustaining a BPBP in the setting of shoulder dystocia decreased from 10.7% in 1997 to 8.3% in 2012 (P=0.006). Birth hypoxia was independently associated with BPBP (OR, 3.1; P<0.001). Cesarean delivery (OR, 0.16; P<0.001) and multiple gestation birth (OR, 0.45; P<0.001) were associated with lower incidence of BPBP. Notably, the rate of cesarean delivery increased by 62.8% during the study period, from 20.9% in 1997 to 34.0% in 2012 (P<0.001). Conclusions: Over a 16-year period, the incidence of BPBP fell dramatically, paralleled by a significant increase in the rate of cesarean delivery. Systemic changes in obstetric practice may have contributed to these trends. As more than half of BPBP cases have no identifiable risk factor, prospective investigation of established risk factors and characterization of new disease determinants are needed to more reliably identify infants at greatest risk. Racial and geographic inequalities in disease burden should be investigated to identify interventional targets.