After years of declines in sudden unexpected infant deaths (SUID), rates have been ticking up again, particularly among babies born to Black mothers, new research shows.
The findings, published Sept. 22 in the journal JAMA Network Open , help explain a puzzling widening of the disparity in infant mortality rates between white and Black populations since 2020.
“This study provides evidence that there is an acute crisis right now in sudden unexplained infant death, a category of cause of death that we assumed we got under control a long time ago,” said co-author Leslie Root, a demographer and assistant research professor in the Institute of Behavioral Science at the University of Colorado Boulder.
Mortality rates for babies born to Black mothers are about twice that of babies born to white mothers, a gap that has persisted for decades. Experts point to higher rates of preterm birth among Black women as the primary cause of the gap, and public health campaigns centering around prenatal care and education have worked to address the issue.
But since 2020, the gap has begun to widen again.
To explore why, Root and her co-authors analyzed federal data on nearly 58 million live births from Jan. 1, 2003, to Dec. 31, 2024. The data set included linked birth-and-death certificates for 366,384 infant deaths among non-Hispanic Black mothers and 224,733 non-Hispanic white mothers.
The researchers grouped infants’ gestational age into seven categories, from extremely preterm (28 weeks) to post-term (42 weeks) to compare mortality rates among white and Black infants born at each gestational age. They also divided deaths into 13 categories.
They found that while differences in gestational age at birth still account for the bulk of the infant mortality gap, other factors are playing an increasing role.
SUID — which includes sudden infant death syndrome, accidental suffocation in bed and other unexplained causes, now accounts for more than a third of the disparity, making it the largest single cause-of-death contributor.
“This finding suggests that even if preterm birth disparities were eliminated entirely, a large mortality gap would remain, and sudden unexpected infant death is what is driving the increase,” said Root.
Root said it’s not clear why rates of SUID are rising among infants born to Black mothers while staying relatively flat among whites. But she points out that the increase coincided with the COVID-19 pandemic.
Some recent studies have suggested that off-season resurgences in respiratory infections, including COVID, RSV and Influenza, could be making infants more vulnerable to sudden infant death syndrome and other forms of SUID. Lingering social and economic consequences associated with the pandemic may have also exacerbated health disparities, widening the infant mortality gap.
Root notes that the shift also coincided with an increase in opioid deaths and overdoses among Black Americans, surpassing, for the first time, the rate among white Americans.
In future studies, the team would like to study whether parental opioid use, which can increase risk of SUID, could be a factor. They also want to look at the data around Native American and Alaska Native populations, which were not included in this study.
An estimated 3,400 infants die unexpectedly in the US each year, making SUID a leading cause of death in infants.
Root hopes the findings will prompt more attention to the issue and heighten efforts to prevent it.
“We have come a long way since a few decades ago,” she said, pointing to campaigns urging parents that “back is best” for a baby’s sleep position and heightening awareness of safe crib standards. “That’s why this uptick, and the fact that there is a racial disparity component, is so alarming. We need to address it.”
JAMA Network Open
10.1001/jamanetworkopen.2026.35321
Data/statistical analysis
People
Decomposition of Black and White Infant Mortality Rates
22-Sep-2026