Late Pregnancy β Blocker Exposure and Risks of Neonatal Hypoglycemia and Bradycardia

BACKGROUND AND OBJECTIVES: beta blockers are widely used in the treatment of hypertensive disorders during pregnancy. These medications cross the placenta and may cause physiologic changes in neonates exposed in utero. We sought to define the risks of neonatal hypoglycemia and bradycardia associated with maternal exposure to beta blockers at the time of delivery in a large, nationwide cohort of Medicaid beneficiaries. METHODS: We used a cohort of 2 292 116 completed pregnancies linked to liveborn infants of Medicaid-enrolled women from 2003 to 2007. We examined the risks of neonatal hypoglycemia and neonatal bradycardia associated with maternal exposure to beta blockers at the time of delivery. Propensity score matching was used to control for potential confounders including maternal demographics, obstetric and medical conditions, and exposure to other medications. RESULTS: There were 10 585 (0.5%) pregnancies exposed to beta blockers at the time of delivery. The risk of neonatal hypoglycemia was 4.3% in the beta blocker-exposed neonates versus 1.2% in the unexposed; the risk of neonatal bradycardia was 1.6% in the exposed versus 0.5% in the unexposed. After controlling for confounders, risk remained elevated for both neonatal hypoglycemia and bradycardia among exposed pregnancies versus unexposed (adjusted odds ratio, 1.68, 95% confidence interval, 1.50-1.89 and adjusted odds ratio, 1.29, 95% confidence interval, 1.07-1.55, respectively). CONCLUSION Our findings suggest that neonates born to mothers exposed to beta blockers in late pregnancy, including labetalol, are at elevated risk for neonatal hypoglycemia and bradycardia.