Women with chronic hypertension—high blood pressure present 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 in Chicago. The study, which analyzed more than 44 million U.S. live births from 2018 to 2024, also found that women with Type 1 or Type 2 diabetes before pregnancy had a 48% increased risk of having babies with severe heart defects.
The findings matter because CCHD, the most severe form of congenital heart disease, requires surgery or catheter placement within the first year of life and ongoing cardiac specialty care. Although the absolute risk remains low—nearly 28,000 infants (0.06%) were diagnosed with CCHD—the study’s large scale and nationwide data provide robust evidence linking maternal cardiometabolic health to fetal heart development. The research also revealed that maternal hypertension became increasingly common during the study period, rising nearly 48% from approximately 9.4% of pregnancies in 2018 to 13.9% in 2024. The prevalence of CCHD increased about 10% over the same period, from 5.8 to 6.4 cases per 10,000 births, representing nearly 4,000 infants annually in the U.S.
“These results emphasize the importance of monitoring blood pressure, discussing heart health with clinicians and receiving appropriate care before and during pregnancy to reduce the risk of fetal heart defects,” said study author Saad Ur Rahman, M.D., chief cardiology fellow at Lahey Clinic of Beth Israel Lahey Health in Burlington, Massachusetts. The study specifically examined subtypes 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 study’s implications extend to clinical practice and public health. “This study adds to a growing body of evidence linking maternal health and the intrauterine environment with fetal cardiovascular development,” said 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. She noted that the association was stronger for chronic hypertension than for gestational hypertension, “emphasizing the importance of maternal health even before pregnancy begins.” The High Blood Pressure Guideline from the American Heart Association and American College of Cardiology notes that high blood pressure affects about 16% of pregnancies and is a leading cause of serious complications and death for both pregnant individuals and their infants worldwide.
However, the research has limitations. As an observational study using birth certificate data, it can only identify associations, not causation. The dataset also lacks information on genetic factors, maternal health history, prenatal imaging, timing and severity of hypertension, and whether blood pressure treatment was received or controlled. The findings are considered preliminary until published in a peer-reviewed journal. Rahman said future studies should explore the biological mechanisms behind the link and whether CCHD risk is influenced by the timing, severity, and treatment of high blood pressure during pregnancy.
The research was presented at Scientific Sessions 2026, a premier global exchange of cardiovascular science. The full abstract and the meeting’s Online Program Planner are available. A Spanish news release is also offered. For more information on high blood pressure, visit high blood pressure resources from the American Heart Association.
