Pregnancy amplifies cardiovascular risk equally across ages, study finds

Researchers analyzing nearly 2.7 million pregnancies across eleven U.S. states between 2016 and 2021 have arrived at a finding that upends a long-held assumption about maternal age and heart disease: pregnancy amplifies cardiovascular risk equally across all ages, and older women face more cardiac events during pregnancy not because pregnancy itself becomes more dangerous with age, but because they arrive at pregnancy with weaker hearts to begin with.

The study, published in Nature Communications by researchers at Weill Cornell Medicine, compared each woman's risk of experiencing a major adverse cardiovascular event—blood clots, heart failure, cardiomyopathy—during pregnancy and the postpartum period against her risk during an equivalent stretch of time when she was not pregnant. Among the 2.7 million women with a first recorded pregnancy in the dataset, 12,059 experienced a major cardiovascular event during pregnancy or within the postpartum window, compared to just 1,685 during the control period a year later. That sevenfold increase in relative risk held steady regardless of whether a woman was in her twenties or her forties. The absolute numbers, however, told a different story: while younger women experienced roughly three excess cardiovascular events per thousand pregnancies, by age 44 that figure had climbed to ten per thousand. The difference, the researchers concluded, reflected not pregnancy becoming more treacherous with age, but older women carrying more pre-existing cardiovascular disease into pregnancy.

The human toll was substantial. Among the women who suffered a major cardiovascular event during pregnancy or postpartum, 240 died—accounting for nearly half of all maternal deaths in the study population. Of those who survived, almost one in ten required rehabilitation care, nursing facility placement, or home healthcare afterward. Venous thromboembolism, cardiomyopathy, and heart failure were the most common events. These are not rare complications; they are among the leading causes of maternal death worldwide, responsible for 20 to 30 percent of all pregnancy-related deaths globally.

The finding carries a direct implication for how obstetricians approach pregnancy planning. Current practice often treats youth as a protective factor—the assumption being that a young woman's age alone shields her from pregnancy-related heart complications. The data suggest otherwise. A 40-year-old woman with well-controlled blood pressure and no other cardiovascular risk factors may face lower pregnancy-specific cardiac risk than a 25-year-old with unmanaged hypertension or other baseline heart disease. The researchers noted that among women with one or more comorbidities—hypertension and asthma being the most common—the excess cardiovascular events reached twenty per thousand pregnancies by age 45, a figure that demands explanation, particularly around why asthma appeared so frequently among those with pregnancy-related cardiac complications.

The study also surfaced persistent racial disparities. Black women in the dataset experienced higher rates of cardiovascular events during pregnancy than White women, yet the pregnancy-specific relative risk increase did not vary by race. This pattern suggests that the disparity stems not from pregnancy itself becoming more dangerous for Black women as they age, but from differences in baseline cardiovascular health—likely reflecting broader inequities in access to preventive care, management of chronic conditions, and other social determinants of health.

The researchers drew their data from hospital discharge records across a quarter of the U.S. population, lending the findings substantial weight, though the reliance on diagnosis codes rather than direct clinical assessment introduces some uncertainty. The study also lacked information on medications like aspirin, which doctors commonly prescribe to high-risk pregnant women to prevent complications, leaving open the question of how such interventions might reshape the risk picture.

The practical takeaway is straightforward: obstetricians and gynecologists should shift their focus from maternal age as a risk marker to a more granular assessment of each woman's cardiovascular baseline before pregnancy. Screening for hypertension, diabetes, and other modifiable risk factors, followed by aggressive management, could reduce the burden of pregnancy-related cardiac complications. Age alone, the data now suggest, is a poor guide to who needs that scrutiny.