A nationwide analysis finds that higher minimum wages are associated with lower rates of dangerous pregnancy-related hypertension, pointing to economic policy as a potential lever for improving maternal health.
Study: Minimum Wage Policies and Obstetric Disorders in the U.S. Image credit: Krakenimages.com/Shutterstock.com
In a recent study published in the American Journal of Preventive Medicine, a group of researchers examined whether increases in minimum wage levels are associated with changes in the incidence of maternal hypertensive and other nonfatal obstetric disorders in the United States (U.S.) using state-level data.
Why income inequality matters for maternal health outcomes
Nearly 1 in 12 pregnant women develops a hypertensive disorder in the U.S., and this rate has doubled over the past decade. These hypertensive disorders, including gestational hypertension, preeclampsia, and eclampsia, are among the leading contributors to morbidity and mortality among pregnant women. These conditions have increased over time and affect hundreds of thousands of pregnancies each year.
Rates are higher among women from socially and economically disadvantaged backgrounds, especially among racial and ethnic minority groups. These disorders can cause grave short-term problems such as preterm birth and maternal death, as well as long-term health consequences, including heart disease. Further research is needed to understand how income-related policies impact maternal health outcomes.
Using decades of state data to study pregnancy health
This retrospective, population-based study analyzed annual state-level data from all 50 U.S. states and Washington, DC, from 1992 to 2019. The analysis used 1,428 state-year observations with no missing data. Information on the incidence of nonfatal maternal disorders was obtained from the Global Burden of Disease (GBD) study, which combines multiple clinical and surveillance data sources using standardized methods to ensure comparability across states and time.
State minimum wage data were drawn from the University of Kentucky Center for Poverty Research and linked by state and year to health outcomes. Other economic, policy, and demographic variables were also included based on data from reports by the Kaiser Family Foundation, Centers for Disease Control and Prevention, and Integrated Public Use Microdata Series.
Minimum wage was treated as a continuous measure and then classified into a binary exposure indicating whether a state experienced a year-to-year increase of at least one dollar. The analysis examined several categories of nonfatal maternal disorders, such as hypertensive disorders, pregnancy loss, related conditions, labor complications, hemorrhage, and maternal infections.
The analysis used descriptive statistics and regression models within a generalized difference-in-differences event study framework, adjusting for state and year effects, state-specific time trends, and lagged economic and demographic factors. Accuracy checks and alternative estimators were applied to address potential bias from staggered policy adoption and to strengthen causal interpretation within an observational design.
Higher minimum wages linked to fewer hypertensive pregnancy disorders
The analysis included 1,428 state-year observations covering all U.S. states and Washington, DC, over the study period. In 915 state-years, representing 64% of the sample, the minimum wage was equal to the federal minimum wage, while in 513 state-years, or 36%, the minimum wage was higher than the federal level.
States with minimum wages above the federal level differed systematically from those at the federal minimum. These state-years showed higher Earned Income Tax Credit rates, higher maximum benefits from Temporary Assistance to Needy Families (TANF) and the Supplemental Nutrition Assistance Program (SNAP), and a greater likelihood of Medicaid expansion under the Affordable Care Act (ACA).
Clear differences in maternal health outcomes were observed across these groups. State-years covered by the federal minimum wage saw, on average, a higher rate of maternal hypertensive disorders, at 431 cases per 100,000 women versus 372 cases per 100,000 in state-years with higher minimum wages. Incidence rates of maternal obstructed labor and maternal sepsis were also lower in state-years with higher than federal minimum wages.
In contrast, the incidence of maternal abortion and miscarriage was higher in states with minimum wages above the federal level, a descriptive difference that was not interpreted as causal. Across the whole study period, there were 61 instances in which states implemented a minimum wage increase of at least one dollar.
Cumulative effects of the minimum wage increase in the four years following each policy change were explored through regression-based event study analyses. A one-dollar or greater raise in minimum wage was associated with a significantly lower incidence of maternal hypertensive disorders. For this post-policy period, incidence was lower by 64.8 cases per 100,000 women.
A significant association was also observed for maternal hemorrhage, with a reduction of 27.4 cases per 100,000 women. No statistically significant associations were found for other categories of obstetric disorders or for the combined measure of all maternal disorders. Sensitivity analyses largely supported the main findings for maternal hypertensive disorders.
Results remained consistent when prevalence was used instead of incidence, when exposure was defined as a minimum wage increase of at least 0.75 dollars, and when analyses were restricted to the period from 2000 to 2019. When analyses were limited to 2010 to 2019, estimates were no longer statistically significant for any outcome, even though this period included substantially fewer observations.
Findings for maternal hemorrhage were less robust, with null results observed in several alternative model specifications. All models adjusted for a wide range of economic, demographic, and policy factors and used state-clustered standard errors to account for within-state correlation over time.
Minimum wage increases may improve maternal health at scale
This study showed that state minimum wage increases of one dollar or more were associated with meaningful reductions in maternal hypertensive disorders at the population level. The strongest associations appeared two to four years after policy changes, suggesting effects through improved health before pregnancy rather than during pregnancy itself.
Minimum wage increases were also associated with lower rates of postpartum hemorrhage, although these results were less consistent across models. No significant associations were found for other obstetric disorders after adjustment.
Overall, the results suggest that minimum wage policies may improve maternal health by addressing social and economic determinants. However, the authors note that individual-level data are needed to confirm mechanisms and subgroup effects, with potential implications for reducing pregnancy-related morbidity and mortality in the U.S.
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