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Preterm birth remains a leading cause of infant illness and death in the United States. Long-standing racial and ethnic disparities have been widely reported, yet the role of household income over time has been less clear. A large US population-based cross-sectional study analyzed data from 411,469 mothers of infants aged 2 to 4 months between 2011 and 2021 using the Pregnancy Risk Assessment Monitoring System. The researchers examined trends in preterm birth by income level and explored how these patterns differed across racial and ethnic groups. The study found that preterm birth rates increased among lower-income households over time, and that racial disparities persisted across all income levels.
Preterm birth, defined as birth before 37 weeks of gestation, affects families across the country. However, not all families are affected equally. This study focused on preterm birth rates in relation to household income and race and ethnicity. Understanding these patterns can help explain why some groups remain at higher risk.
The researchers used nationally representative US data collected from 2011 to 2021. Household income was grouped by percentage of the federal poverty level. The team analyzed trends over time and examined whether income, race, and ethnicity were associated with differences in preterm birth rates.
After adjusting for maternal age, education, insurance status, health conditions, and prenatal care, household income remained associated with preterm birth. From 2011 to 2021, preterm birth rates increased significantly among households with incomes less than 100 percent and between 100 and 199 percent of the federal poverty level, while rates among households with incomes at or above 200 remained largely stable.
Among non-Hispanic white mothers, higher household income was linked to lower risk of preterm birth compared with lower income after adjustment for covariates, illustrating a clear income gradient. When race and ethnicity were included in the model, the association between income and preterm birth attenuated to the null, indicating that race and ethnicity strongly moderate the relationship between income and preterm birth.
Across all income categories, non-Hispanic Black mothers had the highest preterm birth rates. Even in the highest income group, non-Hispanic Black Mothers had a 13 percent greater risk of preterm birth compared to non-Hispanic white mothers, and in the lowest income group the disparity increased to a 19 percent greater risk. Within the same income categories, Hispanic mothers did not experience significantly higher adjusted risks of preterm birth compared with non-Hispanic white mothers.
These findings highlight that income alone does not fully explain disparities in preterm birth. Racial and ethnic differences persisted even at higher income levels, suggesting that broader structural factors play an important role. The authors point to unequal access to quality health care, cumulative stress, racism and other systemic inequities as potential contributors to these persistent gaps.
Taken together, the results indicate that reducing preterm birth rates will likely require more than income-based interventions alone. While the study does not assess specific prevention strategies, it underscores the importance of approaches that address structural determinants of maternal health alongside economic support. The authors further emphasize the need for improved data collection on preconception health and relevant exposures, better use of electronic medical records, and greater collaboration across health systems to better understand and address these disparities.
Paper available at: Trends in US Preterm Birth Rates by Household Income and Race and Ethnicity | Pediatrics | JAMA Network Open | JAMA Network
Full list of authors: Cordova-Ramos, E.G.; Ruiz, S.Y.; Guyol, G.G.; Kalluri, N.S.; Elansary, M.; McConnell, M.; Parker, M.G.
DOI: 10.1001/jamanetworkopen.2025.50664
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