Even with modern prenatal care, thousands of U.S. families each year experience the heartbreak of stillbirth, and a surprising number happen without warning.

A study, published Monday in JAMA, analyzed nearly 2.8 million pregnancies and found that about 30% of stillbirths occurred with no clear medical cause or risk factor.

Researchers from the Harvard T.H. Chan School of Public Health and Mass General Brigham said their findings highlight major disparities that continue to affect Black families and low-income communities.

"Even when we know someone is at increased risk, our tools for prevention are still limited," co-author Dr. Mark Clapp, an obstetrician at Massachusetts General Hospital, told The Washington Post. "Every stillbirth represents an unimaginable loss, not just for the mother but for the entire family, and is a reminder of how far we still have to go."

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