Brachial Plexus Birth Injury in Elective Versus Emergent Caesarean Section: A Cohort Study.

OBJECTIVE: Although Caesarean section (CS) is protective for brachial plexus birth injury (BPBI), the incidence is not zero. A trial of labour with unfavourable intrauterine positioning is hypothesized to result in excessive force on the brachial plexus. The purpose of this study was to determine the risk of BPBI in emergent CS versus elective CS. METHODS: This was a retrospective cohort study. The authors used a nationwide demographic sample of all infants born in Canada from 2004 to 2012. BPBI diagnoses, risk factors, and national incidence data were obtained from the Canadian Institute for Health Information Discharge Abstract Database and Hospital Morbidity Database. The primary outcome was risk of BPBI in emergent CS versus elective CS. RESULTS: BPBI incidence was 1.24 per 1000 live births. Known biases may have underestimated the incidence. CS (elective and emergent) was protective for BPBI as compared with vaginal delivery (odds ratio [OR] 0.15; 95% confidence interval [CI] 0.13-0.18, P < 0.0001). Emergent CS was a moderately strong risk factor for BPBI versus elective CS (OR 3.14; 95% CI 1.79-5.10, P = 0.0001). CONCLUSION: Emergent CS is a moderate risk factor for BPBI compared with elective CS. Intrauterine positioning with a trial of labour may provide an antenatal etiology in these distinct cases.