(A-291) Antihypertensive medication use, type of hypertension, and risk of birth defects: Expanded results from the National Birth Defects Prevention Study (1997-2011) and Birth Defects Study to Evaluate Pregnancy exposureS (2014-2021)

Background: Our previous analyses of National Birth Defects Prevention Study (NBDPS) data (1997-2011) observed increased risk of certain birth defects associated with maternal first trimester antihypertensive medication use, but uncontrolled confounding by type of hypertension among those diagnosed was a noted limitation.

Objectives: This analysis adds 7 years of data for the association between self-reported antihypertensive medication use and selected defects and incorporates additional information on type of hypertension (gestational, pre-gestational, or none).

Methods: We analyzed data from 32,692 mothers of cases and 13,659 mothers of controls who participated in the NBDPS (1997-2011 estimated delivery dates, or EDDs) and the Birth Defects Study to Evaluate Pregnancy exposureS (BD-STEPS; 2014-2021 EDDs). Participants with 2006-2021 EDDs reported hypertension type; we used multiple imputation to impute hypertension type for participants missing this information. We used multivariable logistic regression to estimate odds ratios (OR) and 95% confidence intervals (CI) for the association between self-reported antihypertensive medication use in early pregnancy and 41 specific birth defects, controlling for hypertension type, age at delivery, race/ethnicity, body mass index, parity, pregestational diabetes, and study site. We imputed hypertension type for 29.8% of controls and 38.7% of cases.

Results: Although we observed elevated ORs for most of the birth defects we analyzed, all CIs except those for anencephaly (OR 2.8, 95% CI 1.3-5.7) and coarctation of the aorta (1.7, 95% CI 1.1-2.6) included 1.0. ORs estimated were generally attenuated compared to our previously published results, and elevated ORs were observed across all body systems.

Conclusions: These results suggest that type of hypertension may account for some, but not all, of the previously observed associations between antihypertensive medication use and birth defects. Further analysis of the severity of underlying hypertension is needed to more fully understand whether antihypertensive medication use is independently associated with increased risk of birth defects.