Women with high blood pressure before pregnancy or diagnosed before 20 weeks of pregnancy, known as chronic hypertension, were associated with a 30% higher risk of delivering an infant with critical congenital heart disease (CCHD), according to preliminary research presented at the American Heart Association's Scientific Sessions 2026. The study, which analyzed health data for more than 44 million U.S. 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 compared to women without diabetes.
CCHD is the most severe form of congenital heart disease, and infants affected require surgery or catheter placement during their first year of life and continued cardiac specialty care. The analysis 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 also increased about 10% during the same timeframe, from 5.8 cases per 10,000 births in 2018 to 6.4 cases per 10,000 births in 2023-2024, representing nearly 4,000 infants in the U.S. each year.
The study explored various types of high blood pressure in pregnancy, including gestational hypertension, which was linked to an 8% increased likelihood of CCHD, and eclampsia, which was not significantly associated with CCHD. 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 health 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 in the division of cardiovascular medicine 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."
The study used the CDC's National Vital Statistics System, a nationwide database of U.S. birth-certificate records, and adjusted for factors such as maternal demographics, diabetes, smoking status, pregnancy history, and pregnancy length. The authors noted that the observational design limits conclusions to identifying associations rather than direct causation, and that birth certificate data does not capture genetic factors, maternal health history, prenatal imaging, or details about blood pressure treatment and control.
Flora Nuñez Gallegos, M.D., M.P.H., a pediatric cardiologist at University of California San Francisco and a member of the American Heart Association's Council on Lifelong Congenital Heart Disease and Heart Health in the Young, commented, "This study adds to a growing body of evidence linking maternal health and the intrauterine environment with fetal cardiovascular development. Although the absolute risk of critical congenital heart disease remains low, these findings highlight the importance of identifying and managing chronic hypertension before and during pregnancy." The full abstract and the Online Program Planner are available. A Spanish news release is also available.
The findings underscore the need for preconception counseling and careful management of chronic conditions to potentially reduce the risk of severe congenital heart defects. As the prevalence of maternal hypertension continues to rise, these results may inform clinical practice and public health strategies aimed at improving maternal and infant outcomes. The American Heart Association provides resources such as Preeclampsia and High Blood Pressure and a Preeclampsia, High Blood Pressure and Maternal Health fact sheet for further information.
