Women with high blood pressure before pregnancy or diagnosed before 20 weeks of pregnancy—known as chronic hypertension—face a 30% higher risk of delivering 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 analysis of 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 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 out of more than 44 million births, or 0.06%, representing almost 4,000 infants in the U.S. each year. Approximately 1.5% of CCHD cases were linked to chronic or gestational hypertension. Gestational hypertension, diagnosed at 20 weeks or later, was associated with an 8% increased likelihood of CCHD, while eclampsia showed no significant association.
The implications extend beyond individual pregnancies. Maternal hypertension became increasingly common during the study period, rising nearly 48% from about 9.4% of pregnancies in 2018 to 13.9% in 2024. Over roughly the same period, CCHD prevalence increased about 10%, from 5.8 to 6.4 cases per 10,000 births. 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 and death for both pregnant individuals and their infants worldwide.
“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., chief cardiology fellow at Lahey Clinic of Beth Israel Lahey Health in Burlington, Massachusetts. “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.”
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, noted that while the absolute risk of CCHD remains low, the stronger association for chronic hypertension than for gestational hypertension highlights the importance of maternal health even before pregnancy begins. The study authors called for future research into the biological mechanisms linking maternal high blood pressure to CCHD and whether risk is influenced by the timing, severity and treatment of hypertension.
The observational study used the CDC’s National Vital Statistics System natality files and adjusted for factors such as maternal demographics, diabetes, smoking status and pregnancy length. Limitations include the use of birth certificate data, which does not capture genetic factors, maternal health history, prenatal imaging or blood pressure treatment and control. As an abstract presented at a scientific meeting, the findings are considered preliminary until published in a peer-reviewed journal. The research was announced via NEWMEDIAWIRE.
