By A comprehensive study led by researchers from the Harvard T.H. Chan School of Public Health and Mass General Brigham has found that stillbirth rates in the United States are significantly higher than earlier estimates suggested. The findings also reveal that while most stillbirths are associated with at least one identifiable medical risk factor, a considerable portion occur in pregnancies with no known risks — particularly those reaching or surpassing 40 weeks of gestation.
Stillbirths continue to affect roughly 21,000 families each year across the United States. Alarmingly, experts estimate that more than half of those occurring at 37 weeks or later could be preventable. Despite this, research into the underlying causes of stillbirth remains limited.
“Our study highlights the pressing need to improve stillbirth risk prediction and prevention,” said Jessica Cohen, co-senior author and professor of health economics at Harvard Chan.
The findings were published in JAMA and mark one of the largest and most detailed examinations of the stillbirth burden ever conducted in the U.S.
Analyzing More Than 2.7 Million Pregnancies
The research team analyzed data from nearly 2.7 million pregnancies between 2016 and 2022. Drawing from multiple national datasets — including the Health Care Cost Institute, the American Community Survey, and the March of Dimes — researchers identified 18,893 stillbirths during the six-year study period.
To better understand the factors involved, they examined correlations between stillbirths and a wide range of clinical, obstetric, and socioeconomic conditions.
The clinical risk factors assessed included gestational age, fetal movement and growth patterns, fetal abnormalities, and maternal health conditions such as obesity, gestational and chronic hypertension, pregnancy-related diabetes, pre-pregnancy diabetes, and substance use. Obstetric factors such as a previous stillbirth, poor pregnancy outcomes, and abnormal amniotic fluid levels were also considered.
Socioeconomic indicators — including income levels, race, access to obstetric care, and rural versus urban location — were analyzed to identify potential disparities in stillbirth outcomes across U.S. communities.
Higher Than Reported National Averages
The study’s results reveal that nearly one in every 150 births in the U.S. ends in stillbirth — a rate higher than the Centers for Disease Control and Prevention (CDC) figure of one in 175 births.
In low-income regions, the rate climbed to one in 112 births, highlighting a troubling socioeconomic divide. Areas with a higher percentage of Black families faced even greater risk, with stillbirths occurring in one out of every 95 deliveries.
Interestingly, the study found that geographic location and access to obstetric care did not significantly influence the overall stillbirth rate — suggesting that other underlying social and medical disparities may be at play.
Many Stillbirths Occur Without Known Risk Factors
Although 72.3% of stillbirths in the study were linked to at least one identifiable risk factor, nearly 27.7% occurred with no apparent cause. The absence of risk factors became more common as pregnancies progressed to full term or beyond.
At 38 weeks, 24.1% of stillbirths had no clinical risk factor; this rose to 34.2% at 39 weeks, and 40.7% at 40 weeks or later. Among the cases with identifiable risks, low amniotic fluid levels, fetal abnormalities, and chronic hypertension were most strongly associated with stillbirth.
These findings underscore the need for more refined monitoring techniques and improved prediction tools for late-term pregnancies — especially those that appear clinically normal.
Persistent Disparities and the Need for Policy Action
“Although momentum toward improving stillbirth research and prevention efforts has increased in recent years, rates in the United States remain much higher than in peer countries,” said Dr. Mark Clapp, co-senior author and maternal-fetal medicine specialist in the Department of Obstetrics and Gynecology at Massachusetts General Hospital.
“I hope this study will inform policy, practice changes, and future research to ensure no person or family has to experience this outcome,” Clapp added.
The research team emphasized the urgent need to explore the societal, healthcare system, and clinical factors contributing to these disparities. They also called for increased funding and public health initiatives aimed at reducing stillbirth rates nationwide.
A Call for Deeper Understanding
The study’s lead author, Haley Sullivan, a Ph.D. candidate in Health Policy at Harvard, said the results point to the complex interplay between health, environment, and socioeconomic conditions in determining pregnancy outcomes.
Co-author Anna Sinaiko of Harvard Chan added that the data demonstrate a pressing need to expand stillbirth prevention research and implement strategies that address both medical and social inequities.
Looking Ahead
While advances in prenatal care and technology have improved maternal and fetal health outcomes in recent decades, the study highlights that stillbirth remains a persistent and often overlooked public health challenge in the U.S.
By drawing attention to previously unrecognized patterns and risk factors, researchers hope their findings will guide new screening protocols, healthcare policies, and community-based interventions aimed at preventing stillbirths — particularly in underserved populations.
As the authors conclude, understanding and addressing the multifaceted causes behind these tragic losses is essential to ensuring that fewer families face the heartbreak of stillbirth in the years to come.
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