1. State Medicaid expansion was not associated with differences in overall rates of low birth weight or preterm birth outcomes.
2. There were improvements in relative disparities for black infants compared with white infants among the states that expanded versus the states that did not.
Evidence Rating Level: 2 (Good)
Study Rundown: Since 1990, states have been required to provide Medicaid coverage to pregnant women with family incomes up to 133% of the federal poverty level. Under the Affordable Care Act (ACA), states may expand Medicaid to adults with household incomes at or below 138% of the federal poverty level. Based on data from 2011-2016, state Medicaid expansion was not significantly associated with differences in rates of low birth weight or preterm birth outcomes. However, there were significant improvements in relative disparities for black infants compared with white infants in states that expanded Medicaid compared to those that did not.
Though this study suggests Medicaid expansions had minimal effects on neonatal health, this study has limitations. There was probable selection bias in using the Birth Data Files database, which may have missing data on maternal factors potentially related to birth outcomes. Second, it may take more time for the benefits of health insurance coverage to improve maternal health and access to care.
Relevant Reading: Medicaid expansion and infant mortality in the United States
In-Depth [cross-sectional study]: This was an observational study of 15,631,174 live US births (~99% of all US births) from 2011 to 2016. A difference-in-differences (DID) approach was used to compare changes in outcomes in expansion vs non-expansion states. A difference-in-difference-in-differences (DDD) approach was used to assess the change in birth outcomes for minority infants in expansion states relative to non-expansion states compared with the change in birth outcomes for white infants. The outcomes were preterm birth (<37 weeks gestation), very preterm birth (<32 weeks gestation), low birth weight (<2500 g), and very low birth weight (<1500 g). The adjusted DID estimate for all 4 outcomes was not statistically significant, indicating no association of Medicaid expansion with preterm birth (0.00%; CI95 −0.14 to 0.15%), very preterm birth (−0.02%; CI95 −0.05 to 0.02%), low birthweight (−0.08%; CI95 −0.20 to 0.04), or very low birthweight (−0.03%; CI95 −0.06 to 0.01%). Disparities for black infants relative to white infants in Medicaid expansion states compared with non-expansion states declined for all 4 outcomes, indicated by a negative adjusted DDD coefficient for preterm birth (−0.43%; CI95 −0.84 to −0.02%), very preterm birth (−0.14%; CI95, −0.26 to −0.02%) low birth weight (−0.53% CI95 −0.96 to −0.10%), and very low birth weight (−0.13%; CI95 −0.25 to −0.01%).
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