Chronic hypertension in pregnancy and the risk of congenital malformations: a cohort study.

OBJECTIVE Chronic hypertension is a common medical condition in pregnancy. The purpose of the study was to examine the association between maternal chronic hypertension and the risk of congenital malformations in the offspring. STUDY DESIGN We defined a cohort of 878,126 completed pregnancies linked to infant medical records using the Medicaid Analytic Extract. The risk of congenital malformations was compared between normotensive controls and those with treated and untreated chronic hypertension. Confounding was addressed using propensity score matching. RESULTS After matching, compared with normotensive controls, pregnancies complicated by treated chronic hypertension were at increased risk of congenital malformations (odds ratio [OR], 1.3; 95% confidence interval [CI], 1.2-1.5), as were pregnancies with untreated chronic hypertension (OR 1.2; 95% CI, 1.1-1.3). In our analysis of organ-specific malformations, both treated and untreated chronic hypertension was associated with a significant increase in the risk of cardiac malformations (OR, 1.6; 95% CI, 1.4-1.9 and OR, 1.5; 95% CI, 1.3-1.7, respectively). These associations persisted across a range of sensitivity analyses. CONCLUSION There is a similar increase in the risk of congenital malformations (particularly cardiac malformations) associated with treated and untreated chronic hypertension that is independent of measured confounders. Studies evaluating the teratogenic potential of antihypertensive medications must control for confounding by indication. Fetuses and neonates of mothers with chronic hypertension should be carefully evaluated for potential malformations, particularly cardiac defects.