Published in
JAMA Network Open, the study by Erika G. Cordova-Ramos of Boston Medical Center and colleagues assessed decade-long trends in preterm birth in the United States, focusing on household income and the role of race and ethnicity. Although racial disparities in preterm birth are well recognized, the authors highlighted limited evidence on how income-related patterns have changed over time and whether higher income offers equal protection across racial groups.
The analysis used data from the nationally representative Pregnancy Risk Assessment Monitoring System and included 411,469 mothers, representing about 20 million mother–infant pairs from 2011 to 2021. Household income was classified relative to the federal poverty level into three categories: below 100%, 100% to 199%, and 200% or higher. Preterm birth was defined as delivery before 37 weeks of gestation.
The key findings of the study were as follows:
- Preterm birth rates increased significantly over the 10 years among families with lower incomes, rising from 9.7% in 2011 to 11.1% in 2021 among households earning less than 100% of the federal poverty level.
- A similar upward trend was observed among households earning 100% to 199% of the federal poverty level, with preterm birth rates increasing from 7.8% to 10.0% during the study period.
- In contrast, preterm birth rates remained largely stable among households with incomes at or above 200% of the federal poverty level.
- Racial and ethnic disparities in preterm birth were observed across all income groups, with non-Hispanic Black mothers consistently experiencing the highest rates regardless of household income.
- For most racial and ethnic groups, preterm birth was most common among families living below the poverty line, with Asian mothers representing an exception to this pattern.
- While lower income was initially linked to a higher risk of preterm birth, this association diminished after adjustment for race and ethnicity, indicating a strong moderating effect of race.
- Disparities persisted even within income categories, with non-Hispanic Black mothers in the lowest income group having a 19% higher risk of preterm birth compared with non-Hispanic White mothers.
- Elevated risk among non-Hispanic Black mothers was also evident in higher-income households, where they had a 13% greater risk of preterm birth than non-Hispanic White mothers.
The authors acknowledged limitations, including reliance on self-reported income data and the cross-sectional design, which precludes causal conclusions. Nevertheless, the findings point to widening income-related gaps and enduring racial inequities in preterm birth.
The researchers emphasized that addressing poverty alone is unlikely to close these gaps, highlighting the need to confront structural factors, including racism, that jointly shape adverse birth outcomes in the United States.
Reference:
Cordova-Ramos EG, Ruiz SY, Guyol GG, et al. Trends in US Preterm Birth Rates by Household Income and Race and Ethnicity. JAMA Netw Open. 2026;9(1):e2550664. doi:10.1001/jamanetworkopen.2025.50664
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