Background Many states expanded Medicaid eligibility under the Patient Protection and Affordable Care Act (PPACA). Medicaid expansion might impact infant mortality through improved maternal health prior to pregnancy and reduced insurance churn. Some studies suggest the PPACA had no significant impact on low birth weight or preterm birth, while others suggest that the PPACA led to a significant decrease in infant mortality.

Methods Using a difference-in-differences estimator with fixed effects to control for differences in state characteristics and time trends we analyse three samples of births from the CDC’s linked birth/death files from 2011 to 2017 to estimate the impact of Medicaid expansion on infant mortality.

Results We find mixed results. In our full sample, we find no statistically significant change in infant mortality associated with PPACA Medicaid expansion. However, when we restrict the sample to states who had adopted the 2003 birth certificate form and when we further exclude states with a Medicaid waiver, in both samples we see reductions in infant mortality for babies born to mothers of all races. When we stratify by race, we find infant mortality decreased for babies born to white mothers. However, this decrease is not seen for babies born to black mothers.

Conclusions Medicaid expansion under the PPACA has an impact on infant mortality, but the results are sensitive to the sample of states included in the study. There is suggestive evidence that Medicaid expansion is not closing the infant mortality gap between black and white babies.