Women with chronic hypertension—defined as high blood pressure before pregnancy or diagnosed before 20 weeks of gestation—were 30% more likely to deliver an infant with critical congenital heart disease (CCHD) compared to women with normal blood pressure, according to preliminary research presented at the American Heart Association’s Scientific Sessions 2026. The analysis of more than 44 million U.S. births from 2018 to 2024 also found that women with Type 1 or Type 2 diabetes prior to pregnancy had a 48% increased risk of having babies with severe heart defects.
CCHD is the most severe form of congenital heart disease, requiring surgery or catheter placement within the first year of life and ongoing cardiac specialty care. The study identified nearly 28,000 infants with CCHD, representing about 6.4 cases per 10,000 births in 2023-2024—roughly 4,000 infants annually in the U.S.
The findings matter because maternal hypertension is becoming more common. The prevalence rose nearly 48%, from approximately 9.4% of pregnancies in 2018 to 13.9% in 2024, while CCHD prevalence increased about 10% over the same period. “Our findings suggest that maternal heart health before and during pregnancy may have a particularly important relationship with fetal heart development,” said study author Saad Ur Rahman, M.D., a chief cardiology fellow at Lahey Clinic of Beth Israel Lahey Health. He emphasized the importance of monitoring blood pressure and receiving appropriate care before and during pregnancy.
The study examined several types of high blood pressure in pregnancy, including chronic, gestational, and eclampsia. Gestational hypertension was associated with an 8% increased likelihood of CCHD, while eclampsia was not significantly associated with the condition. The stronger association for chronic hypertension highlights the importance of maternal health even before pregnancy begins, noted Flora Nuñez Gallegos, M.D., M.P.H., a pediatric cardiologist at the University of California San Francisco and a member of the American Heart Association’s Young Hearts Council.
According to the American Heart Association/American College of Cardiology 2025 High Blood Pressure Guideline, high blood pressure affects approximately 16% of pregnancies and is a leading cause of serious complications for both mothers and infants. The researchers used the CDC’s National Vital Statistics System and adjusted for factors such as demographics, diabetes, smoking, and pregnancy history. However, the observational design limits conclusions to associations rather than causation, and birth certificate data may not capture genetic factors, timing of hypertension, or treatment details.
Rahman called for future studies to explore the biological mechanisms linking maternal high blood pressure to CCHD and to examine whether risk is influenced by the timing, severity, and treatment of hypertension. The findings add to a growing body of evidence connecting maternal health and the intrauterine environment with fetal cardiovascular development. More information is available in the release link and the abstract.
