AHA: Hypertension Before Pregnancy Increases the Risk of Congenital Heart Defects in Babies by 30%

The researchers analyzed data on more than 44 million live births in the United States between 2018 and 2024. During this period, nearly 28,000 babies were diagnosed with critical congenital heart defects—the most severe abnormalities, which typically require surgery or a catheter-based intervention within the first year of life.

Chronic hypertension—high blood pressure that existed before pregnancy or was diagnosed within the first 20 weeks—showed the strongest association with the risk of these defects. Women with this condition were 30% more likely to have a baby with a critical heart defect than women without hypertension. In cases of gestational hypertension, which develops after the 20th week of pregnancy, the risk was 8% higher. Eclampsia showed no statistically significant association with congenital heart defects.

The authors also found that women with type 1 or type 2 diabetes diagnosed before pregnancy had a 48% higher risk of having a baby with a critical congenital heart defect.

The researchers emphasize that the study identifies an association but does not prove that hypertension or diabetes directly causes birth defects. Other factors that could not be accounted for, including genetic characteristics and maternal treatment, may also have influenced the results.

Nevertheless, the findings highlight the importance of managing chronic conditions even before pregnancy is planned. The authors say further research is needed to determine the biological mechanisms that may explain the observed association and whether the risk is influenced by the severity of hypertension, when it develops and how it is treated.