Research conducted by experts at Boston Medical Center, in collaboration with the University of Massachusetts Chan Medical School and the Harvard T.H. Chan School of Public Health, reveals a troubling increase in preterm birth rates in the United States. Between 2011 and 2021, households earning less than 200% of the federal poverty level experienced rising rates of preterm births, while rates remained stable among higher-income households. The findings highlight significant racial disparities, with Black mothers facing the highest preterm birth rates across all income categories.
Preterm birth, defined as delivery before 37 weeks of gestation, is a leading cause of infant mortality and morbidity in the United States. Previous studies have established that Black individuals have about twice the risk of preterm birth compared to their white counterparts—a disparity that has persisted for decades. The intersection of household income with race and ethnicity appears to play a critical role in influencing preterm birth risks through various factors, including neighborhood conditions, access to nutritious food, quality healthcare, exposure to environmental pollutants, and the effects of chronic stress.
Study Overview and Findings
The study titled “Trends in US Preterm Birth Rates by Household Income and Race and Ethnicity,” published in JAMA Network Open, utilized nationally representative data to investigate trends in preterm birth from 2011 to 2021 among 411,469 mothers and their infants. The analysis categorised race and ethnicity into groups including American Indian or Alaska Native, Asian, Hispanic, non-Hispanic Black, non-Hispanic white, and other or multiracial.
Data for the study were drawn from the Pregnancy Risk Assessment Monitoring System (PRAMS), a perinatal surveillance system developed by the Centers for Disease Control and Prevention (CDC). Mothers completed surveys two to four months postpartum, allowing researchers to link responses with birth certificate data to gain insights into demographics, pregnancy characteristics, and infant outcomes.
Participants reported household income in categorical ranges, with a conservative estimation of income status calculated based on the upper value of each income band. For context, the 2025 poverty guideline for a one-person household was $15,650, while for a three-person household, it was $26,650. Income groups were defined as below 100% of the federal poverty level, 100%–199%, and 200% or more.
During the years studied, preterm birth rates averaged 10.4% for households below 100% of the poverty level, 8.9% for those earning 100%–199%, and 7.5% for households above 200%. Notably, from 2011 to 2021, preterm birth rates in households under 100% increased from 9.7% to 11.1%, while those in the 100%–199% category rose from 7.8% to 10.0%. In contrast, rates for households at 200% or more remained relatively stable, measuring 8.0% in 2011 and 8.1% in 2021.
Racial Disparities and Recommendations
The analysis revealed that Black mothers consistently exhibited the highest preterm birth rates across all income levels. Adjusted models indicated that Black mothers at the lowest income level had a 19% higher relative risk for preterm birth compared to white mothers. Even in the highest income group, Black mothers faced a 13% higher risk. Differences in middle-income groups were not statistically significant.
The study’s authors concluded that disparities in preterm birth linked to household income have widened over the past decade. They emphasized the need to consider how racism and racial inequality contribute to these disparities. They argue that public health efforts aimed at reducing preterm births may fall short if they focus solely on income without addressing the underlying factors of socioeconomic and structural inequities affecting Black communities.
To effectively tackle these issues, the authors advocate for policies and interventions that enhance access to timely and comprehensive prenatal care, address chronic health conditions among mothers, reduce stress, and combat racial and ethnic discrimination in healthcare settings.
The findings of this study bring to light the urgent need for a multifaceted approach to address the rising preterm birth rates in the United States, particularly among vulnerable populations.
