To identify the association of the Affordable Care Act's Medicaid expansion with payment for delivery, early access to prenatal care, preterm birth, and birth weights considered small for gestational age (SGA).
A difference-in-difference design was used to assess changes in outcomes before and after Medicaid expansion in expansion states, using nonexpansion states as a control group. We used national birth certificate data from 2009 to 2017. Difference-in-difference linear probability models were used to assess the effects of the policy implementation, adjusting for demographics, month of birth, state, year, and county-level unemployment rates. Standard errors were clustered at the state level. Two prespecified subgroup analyses were performed of nulliparous women and women with no more than a high school diploma.
The study sample included 8,701,889 women from 15 expansion states and 9,509,994 from 11 nonexpansion states. In the adjusted analysis, the percentage of Medicaid-covered deliveries increased by 2.3 absolute percentage points (95% CI 0.2-4.4, P=.04) in expansion states compared with nonexpansion states. There were no significant changes in the proportion of women who were uninsured, as there was a relative decrease in the percentage of deliveries covered by private insurance (-2.8 percentage points [95% CI -4.9 to -0.8, P=.01]). There were also no significant differences in the rate of women initiating prenatal care in the first trimester, preterm birth rates, or rates of low birth weight after the Medicaid expansion. Findings were similar in both subgroups.
Medicaid expansion was associated with increased Medicaid coverage for childbirth in expansion states; similar gains in private coverage were seen in nonexpansion states. There were no associations with changes in early access to prenatal care, preterm birth, or SGA birth weights.