Where a mother was born matters for her baby’s chances of surviving their first year of life, a new study led by McMaster University shows. The findings reveal a clear and striking disparity: babies born to U.S.-born mothers die at higher rates than of foreign-born mothers.
The research, published Jan. 6, 2026, in JAMA Network Open, found babies of American-born mothers to have a significantly higher risk of dying in their first year compared to those born to moms who were not born in the United States.
The difference in risk was highest when a baby was born full-term among those who were Black, Hispanic, white and multiracial.
The findings raise urgent questions about health behaviours, access to care, and the broader social determinants of health that influence maternal and infant outcomes.
“These findings show that where a mother was born matters for her baby’s survival. Understanding these patterns is crucial for designing interventions that save lives,” says Giulia Muraca, principal investigator and associate professor with McMaster’s Department of Obstetrics and Gynecology.
Researchers used a retrospective, population-based cohort to analyze 25.9 million U.S. births between 2016 and 2022. They used data from the National Vital Statistics System Period/Cohort Linked Birth–Infant Death Data Files, which cover nearly 100 per cent of U.S. births and infant deaths.
The research showed the infant mortality rate was 5.4 deaths per 1,000 births for U.S.-born mothers, compared to 4.0 deaths per 1,000 for babies of foreign-born mothers. In 2022, more than 20,500 infants died in the United States before their first birthday.
A major driver of this trend is sudden unexpected infant death (SUID), which includes sudden infant death syndrome (SIDS), as well as accidental suffocation and strangulation in bed.
Babies of U.S.-born mothers have almost three times higher odds of experiencing SUID. Muraca says more research is needed to better understand why SUID rates are so much higher in babies of U.S.-born mothers.
The higher rate of infant death in U.S.-born mothers also cuts across racial and ethnic groups, with the most pronounced difference occurring in families identifying as Black, Hispanic, white and multiracial.
“Even after accounting for factors like education, insurance, and prenatal care, babies of U.S.-born mothers had significantly higher odds of dying in their first year, especially among full-term births,” Muraca says.
“These findings underscore the urgent need for targeted public health strategies to reduce preventable infant deaths and address the underlying social and structural factors driving these disparities.”
The study was funded in part by a grant from the Canadian Institutes of Health Research and the Marta and Owen Boris Foundation.