Risk factors for brachial plexus injury in a large cohort with shoulder dystocia.

OBJECTIVE: To examine birthweight and other predictors of brachial plexus injury (BPI) among births complicated by shoulder dystocia.

STUDY DESIGN: A retrospective cohort study of term births complicated by shoulder dystocia in California between 1997 and 2006. Birthweight at time of delivery was stratified into 500-g intervals. Women were further stratified by diabetes status, parity, and race/ethnicity. The perinatal outcome of BPI was assessed.

RESULTS: This study included 62,762 deliveries complicated by shoulder dystocia, of which 3168 (5 %) resulted in BPI. The association between birthweight and BPI remained significant regardless of confounders. Each increasing birthweight interval was associated with an increasing risk of BPI compared with 3000-3499-g birthweight. Race/ethnicity, diabetes, and parity were also independently associated with BPI.

CONCLUSION: Increasing birthweight increases the risk of BPI among births with shoulder dystocia, independent of advanced maternal age, race, parity, gestational diabetes, or operative vaginal delivery.