Maternal body-mass-index and neonatal brachial plexus palsy in a California cohort

Objective: To evaluate risk factors and describe the association between maternal pre-pregnancy body-mass-index (BMI) and neonatal brachial plexus palsy (BPP) in vaginal deliveries with and without shoulder dystocia. Methods: This is a retrospective cohort study of singleton, non-anomalous, term vaginal deliveries in California (2007–2011). Deliveries were classified as with or without shoulder dystocia. Our primary outcome was BPP and the independent variable of interest was maternal pre-pregnancy BMI, which was categorized as underweight (<18.5 kg/m²), normal weight (18.5–24.9 kg/m²), overweight (25–29.9 kg/m²), obesity I (30–34.9 kg/m²), obesity II (35–39.9 kg/m²) and obesity III (≥40 kg/m²). We evaluated demographics, maternal, labor, and neonatal characteristics using chi-squared tests and assessed the association of pre-pregnancy BMI with BPP using multivariable logistic regression models. Results: In our cohort of 1,395,761 women, there were 21,463 deliveries with shoulder dystocia and 1,374,298 deliveries without shoulder dystocia. Among deliveries with shoulder dystocia, BPP was observed more frequently in neonates born to women with BMI categorized as overweight (32% vs. 29%; p <.001), obesity I (22% vs. 14%; p <.001), obesity II (10% vs. 6%; p <.001), and obesity III (8% vs. 3%; p <.001). After adjusting for confounders, the odds of BPP in deliveries with shoulder dystocia was significantly higher for women who were overweight (aOR = 1.65; 95% CI: 1.35–2.01), obesity I (aOR = 2.33; 95% CI: 1.86–2.90), obesity II (aOR = 2.56; 95% CI: 1.92–3.40), and obesity III (aOR = 3.80; 95% CI: 2.75–5.25). In deliveries without shoulder dystocia, BPP was more common in women with a BMI that was overweight (29% vs. 25%; p <.001), obesity I (17% vs. 11%; p <.001), obesity II (9% vs. 4%; p <.001), and obesity III (8% vs. 2%; p <.001). In this cohort, multivariable regression model showed similar results in women with a BMI that was overweight (aOR = 1.47; 95% CI: 1.19–1.81), obesity I (aOR = 1.99; 95% CI: 1.55–2.54), obesity II (aOR = 2.79; 95% CI: 2.04–3.83), and obesity III (aOR = 5.05; 95% CI: 3.63–7.03). Conclusion: Rising maternal pre-pregnancy BMI is associated with an increased risk of BPP in vaginal deliveries with and without shoulder dystocia. Preconception interventions targeting weight management may be beneficial in reducing BPP in all deliveries.