Researchers at Boston Medical Center, working with colleagues at University of Massachusetts Chan Medical School and Harvard T.H. Chan School of Public Health report that US preterm birth rates rose from 2011–2021 in households earning less than 200% of the federal poverty level, while remaining stable among higher-income households. Black mothers had the highest preterm birth rates across all income levels.
Preterm birth and inequality
Preterm birth, defined as delivery before 37 weeks’ gestation, remains the leading cause of infant mortality and morbidity in the US. Previous studies have documented about twice the risk of preterm birth among Black individuals compared with white individuals, a disparity unchanged for decades.
Household income often intersects with race and ethnicity and may relate to preterm birth risk through neighborhood environments, access to nutritious food, quality of health care, exposure to pollutants, and burdens tied to chronic conditions and chronic stress.
National trends of preterm birth by household income, plus the extent to which income–based patterns differ within racial and ethnic groups, have been largely unexplored.
Tracking births across a decade
In the study, “Trends in US Preterm Birth Rates by Household Income and Race and Ethnicity,” published in JAMA Network Open, researchers used nationally representative data to examine preterm birth trends by household income from 2011 to 2021 and to examine associations between income and preterm birth across racial and ethnic groups for 411,469 mothers and their babies.
Race and ethnicity categories included American Indian or Alaska Native, Asian, Hispanic, non-Hispanic Black, non-Hispanic white, and other race or multiracial.
Analysis drew on the Pregnancy Risk Assessment Monitoring System (PRAMS), a CDC-developed, multistate, cross-sectional perinatal surveillance system administered by state health departments. Mothers completed PRAMS surveys at two to four months postpartum, and responses, linked with birth certificate data, provided additional demographics, pregnancy characteristics and infant outcomes.
Mothers reported annual household income in categorical ranges, then income status was conservatively estimated by assuming the upper value of each income band and converting to a percentage of the federal poverty level based on year, state, and household size. Income groups were defined as less than 100% of the federal poverty level, 100% to 199%, and 200% or more.
For perspective, the 2025 guideline for 100% of the federal poverty level was $15,650 for a one-person household and $26,650 for a three-person household.
Patterns across income and race
Preterm birth rates averaged 10.4% among households under 100% of the federal poverty level, 8.9% among households at 100%–199%, and 7.5% among households at 200% or more during 2011–2021.
Rates increased in households under 100% from 9.7% in 2011 to 11.1% in 2021 and increased in households at 100%–199% from 7.8% to 10.0% over the same years. Rates at 200% or more measured 8.0% in 2011 and 8.1% in 2021.
The highest preterm birth rates within most racial and ethnic groups occurred in households under 100%, with Asian people as the only exception. Black mothers had the highest preterm birth rates across all income levels.
Adjusted models linked Black mothers to higher risk compared with white mothers at the lowest income level, with an adjusted relative risk 19% higher, and at the highest income level, with an adjusted relative risk 13% higher. Middle income differences were not significant.
Race and ethnicity were so closely aligned with income in the dataset that when both were placed into the same model, race and ethnicity captured the differences that had been showing up by income group alone.
Black mothers in the highest income group experienced higher preterm birth rates than white mothers in the lowest income group.
Reducing inequities could help
Researchers concluded that household income disparities in preterm birth widened over time and that ethnicity associations between income and preterm birth presented a basis to examine the role of racism and racial inequality in preterm birth disparities.
Public health efforts aimed at reducing preterm birth may fall short if income alone guides intervention design. An approach is suggested that can address socioeconomic factors and structural inequities that disproportionately affect Black communities.
Policies and interventions could attempt to improve access to timely and comprehensive prenatal care, address maternal chronic health conditions, reduce stress, and mitigate racial and ethnic discrimination in health care.
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Publication details
Erika G. Cordova-Ramos et al, Trends in US Preterm Birth Rates by Household Income and Race and Ethnicity, JAMA Network Open (2026). DOI: 10.1001/jamanetworkopen.2025.50664
Sunah S. Hwang, The Intersection of Race and Ethnicity, Income, and Preterm Birth, JAMA Network Open (2026). DOI: 10.1001/jamanetworkopen.2025.50675
Journal information:
JAMA Network Open
The content is provided for information purposes only.