Objectives. To explore the effect of Medicaid expansion on US infant mortality rate.
Methods. We examined data from 2010 to 2016 and 2014 to 2016 to compare infant mortality rates in states and Washington, DC, that accepted the Affordable Care Act Medicaid expansion (Medicaid expansion states) and states that did not (non–Medicaid expansion states), stratifying data by race/ethnicity.
Results. Mean infant mortality rate in non–Medicaid expansion states rose (6.4 to 6.5) from 2014 to 2016 but declined in Medicaid expansion states (5.9 to 5.6). Mean difference in infant mortality rate in Medicaid expansion versus non–Medicaid expansion states increased from 0.573 (P = .08) in 2014 to 0.838 in 2016 (P = .006) because of smaller declines in non–Medicaid expansion (11.0%) than in Medicaid expansion (15.2%) states. The 14.5% infant mortality rate decline from 11.7 to 10.0 in African American infants in Medicaid expansion states was more than twice that in non–Medicaid expansion states (6.6%: 12.2 to 11.4; P = .012).