The effects of the Rx Kids unconditional cash prescription programme during pregnancy and infancy on birth outcomes in the USA: a population-based, quasi-experimental study

BACKGROUND: Rates of preterm birth and low birthweight remain high in the USA, in part due to perinatal poverty and societal underinvestment during a crucial window of human development. In 2024, Rx Kids was launched in Flint, Michigan, providing every expectant mother with unconditional cash transfers during pregnancy and infancy. It is the first cash transfer programme in the USA with universal eligibility (ie, community wide and no means testing) that targets the perinatal period. This study aimed to estimate the impact of Rx Kids on birth outcomes. METHODS: In this population-based study, we used administrative data from the Michigan Department of Health and Human Services for all births in the state of Michigan, USA, and a quasi-experimental study design. Our study population comprised all infants born from Jan 1, 2021, to June 30, 2025, to women aged 16 years and older. The primary outcomes were preterm birth (<37 weeks) and low birthweight (<2500 g). Secondary outcomes included small for gestational age, admission to the neonatal intensive care unit, smoking in the third trimester, and prenatal care adequacy. We used a difference-in-differences strategy to estimate the adjusted mean change for the outcomes in Flint after implementation of Rx Kids relative to changes in a comparison group of matched cities. We also assessed several subgroups and the underlying assumptions of our difference-in-differences strategy. FINDINGS: In 2021-23, the 3 years before the implementation of Rx Kids, 15·1% (445 of 2940) of births in Flint were preterm and 15·8% (465 of 2943) were low birthweight. Relative to the matched cities, Rx Kids was associated with a decrease in the preterm birth rate by 2·7 percentage points (95% CI -4·6 to -0·8; p=0·0075) and in the proportion of infants born with low birthweight by 4·2 percentage points (-6·0 to -2·4; p<0·0001). Corresponding to these reductions, Rx Kids was associated with fewer admissions to the neonatal intensive care unit by 4·4 percentage points (-6·5 to -2·4), less smoking in the third trimester (-1·7 percentage points [-2·4 to -0·9]), and more adequate prenatal care (5·7 percentage points [1·8 to 9·7]). The improvements in low birthweight, very low birthweight, very preterm, smoking in the third trimester, and prenatal care adequacy were most robust to alternative model specifications. The estimates for the primary outcomes were larger in magnitude for women who were non-Hispanic Black, nulliparous, and insured by Medicaid. INTERPRETATION: With significant reductions in adverse birth outcomes, the treatment of perinatal poverty with a place-based intervention as replicable and scalable as Rx Kids has important implications for infants and society. These findings suggest that the economic hardship of the perinatal period, starting in utero, contributes to adverse outcomes and is addressable. FUNDING: Charles Stewart Mott Foundation and the Jamie and Denise Jacob Family Foundation.