Women with chronic hypertension before pregnancy or diagnosed before 20 weeks of pregnancy face a 30% higher risk of delivering an infant with critical congenital heart disease (CCHD), the most severe form of heart defects, compared to women with normal blood pressure, according to preliminary research presented at the American Heart Association’s Scientific Sessions 2026. The study, analyzing 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 prior to pregnancy had a 48% increased risk of having babies with severe heart defects. The findings highlight the importance of managing maternal health before and during pregnancy to reduce the risk of fetal heart defects.
The research used the CDC’s National Vital Statistics System, a nationwide database of birth-certificate records. Among the more than 44 million live births, nearly 28,000 infants (0.06%) were diagnosed with CCHD. Approximately 1.5% of these cases were linked to chronic or gestational hypertension. The study revealed that maternal hypertension became increasingly common during the study period, rising from about 9.4% of pregnancies in 2018 to 13.9% in 2024—a nearly 48% increase. The prevalence of CCHD also increased about 10% during the same period, 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.
“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.”
Gestational hypertension, diagnosed after 20 weeks of pregnancy, was associated with an 8% increased likelihood of CCHD, while eclampsia was not significantly associated with the condition. The study adjusted for factors such as maternal demographics, diabetes, smoking status, pregnancy history and pregnancy length. However, as an observational study using birth certificate data, it could not capture genetic factors, maternal health history, prenatal imaging, timing of hypertension, or treatment details, limiting conclusions to associations rather than causation.
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 findings underscore the need to identify and manage chronic hypertension before and during pregnancy. “The association with an infant’s risk of critical congenital heart disease was stronger for chronic hypertension than for gestational hypertension, emphasizing the importance of maternal health even before pregnancy begins,” she said.
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, according to the American Heart Association/American College of Cardiology 2025 High Blood Pressure Guideline. The study’s abstract is available in the abstract and the Online Program Planner. For more details, see the release link and the Spanish news release. Information on high blood pressure, high blood pressure in pregnancy, chronic and gestational hypertension, eclampsia, and congenital heart disease is available from the American Heart Association. The Association’s financial information is available here.
