Research conducted by the 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 from 2011 to 2021. The study indicates that households earning less than 200% of the federal poverty level experienced a rise in preterm births, while rates remained stable among higher-income households. Moreover, Black mothers consistently exhibited the highest preterm birth rates across all income levels.
Preterm birth, defined as delivery before 37 weeks of gestation, is the leading cause of infant mortality and morbidity in the US. Historical data shows that Black individuals are at a significantly higher risk of preterm birth, approximately twice that of their white counterparts, with this disparity persisting for decades. The intersection of household income, race, and ethnicity is crucial, as these factors influence access to healthcare, nutritious food, and environmental conditions, all of which can affect preterm birth outcomes.
Analyzing Data Over a Decade
The findings, published in the journal JAMA Network Open, examined national trends in preterm birth rates among 411,469 mothers and their infants. Researchers utilized data from the Pregnancy Risk Assessment Monitoring System (PRAMS), a comprehensive surveillance initiative developed by the Centers for Disease Control and Prevention (CDC). By linking survey responses with birth certificate data, they provided insights into the demographics, pregnancy characteristics, and infant outcomes.
Mothers indicated their annual household income within categorical ranges, which were then estimated in relation to the federal poverty level. For context, the guideline for 100% of the federal poverty level in 2025 is projected at $15,650 for a one-person household and $26,650 for a three-person household.
The study identified that preterm birth rates averaged 10.4% among households below 100% of the federal poverty level, 8.9% among those earning between 100% and 199%, and 7.5% among households at 200% or more. Notably, rates for households under 100% increased from 9.7% in 2011 to 11.1% in 2021, while households between 100% and 199% saw an increase from 7.8% to 10.0% during the same period.
Race, Ethnicity, and Preterm Birth Disparities
The analysis highlighted that Black mothers faced the highest preterm birth rates across all income levels. Adjusted models revealed that Black mothers had a 19% higher risk of preterm birth compared to white mothers at the lowest income level, and a 13% higher risk at the highest income level. The middle-income category did not show significant differences.
The dataset’s strong correlation between race and income meant that when both factors were analyzed together, racial disparities became the more prominent focus. Even in the highest income group, Black mothers experienced higher preterm birth rates compared to white mothers in the lowest income bracket.
The researchers concluded that the widening disparities in preterm birth rates highlight the complex interplay of income and ethnicity. They emphasized that public health initiatives aimed at reducing preterm birth must consider not only economic factors but also the structural inequities that disproportionately affect Black communities.
To effectively tackle these disparities, the study suggests promoting policies and interventions that improve access to comprehensive prenatal care, address maternal chronic health conditions, reduce stress, and combat racial discrimination within the healthcare system.
This research underscores the urgent need for a multifaceted approach to address the rising rates of preterm births, particularly among vulnerable populations in the United States.
