Study Finds Medicaid Expansion Not Significantly Associated With Adverse Birth Outcome Rates

Rates of low birth weight and premature birth are higher in the United States than most other developed nations, and these factors are believed to contribute to nearly 36% of infant mortality. A recent study sought to evaluate whether Medicaid expansion was associated with changes in rates of low birth weight and preterm outcomes, both overall and by race/ethnicity.

Researchers compared the differences among births in Medicaid expansion and nonexpansion states, both overall and within each racial/ethnic group in the period prior to expansion using a differences-in-differences (DID) approach. Additionally, 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 nonexpansion states compared with the change in birth outcomes for white infants in expansion states relative to nonexpansion states.”

Researchers evaluated birth outcomes among 15,631,174 singleton live births to women aged 19 years and older. The racial/ethnic subgroups included: 8,244,924 births to white women, 2,201,658 births to black women, and 3,944,665 births to Hispanic women. The births occurred from 2011 to 2016.

The study authors found interesting differences amongst the groups studied. Expansion states had a higher percentage of births covered by private insurance (50.7% vs 43.9%; difference: 6.8 percentage points [95% CI, 6.7-6.9]), a lower percentage of births to mothers who achieved a high school or less education (38.9% vs 41.2%; difference: −2.4 percentage points [95% CI, −2.5 to −2.3]), and a higher percentage of births with prenatal care delivered during the first trimester (77.6% vs 71.9%; difference: 5.7 percentage points [95% CI, 5.7-5.8]).

Additionally, the investigators found that among births of all races/ethnicities, adverse outcomes in expansion states declined for preterm birth (6.80% to 6.67%; difference: −0.12 [95% CI, −0.16 to −0.09]). However, in nonexpansion states, the study found that adverse outcomes increased for low birth weight and very low birth weight (6.06% to 6.18%; difference: 0.11 [95% CI, 0.08-0.15], and 0.88% to 0.90%; difference: 0.02 [95% CI, 0.00-0.03]), respectively. Also, in nonexpansion states, adverse outcomes decreased for preterm birth (7.86% to 7.78%; difference: −0.08 [95% CI, −0.12 to −0.04]).

While researchers explained that there were no significant differences in the change in birth outcomes between expansion and nonexpansion states, the study did find greater reductions in rates of low birth weight and preterm birth outcomes among black infants in expansion states relative to white infants in expansion states, with no significant change in outcome among Hispanic infants.

According to the study, black infants die of complications associated with prematurity and low birth weight at nearly 3.9 times the rate of white infants (257.6 vs 66.3 per 100 000 live births in 2016). Previous studies have suggested that reducing the rates of low birth weight and preterm birth among black infants could be the primary mechanism for decreasing inequities in infant mortality, though notably, this study did not find improvements for Hispanic infants as the findings were not significant, the reasons for which, the authors write, remain unclear.

“The findings here suggest earlier and continual access to insurance coverage may provide an important opportunity for improving infant outcomes. Because low birth weight and premature births are highly related to complex medical comorbidities throughout childhood and into adulthood, the implications of the improvements associated with Medicaid expansion could potentially be associated with reduced disparities in chronic conditions across the life course,” wrote the authors.

Reference

Brown C, Moore J, Felix H, et al. Association of state Medicaid expansion status with low birth weight and preterm birth. JAMA. 2019;321(16):1598-1609. doi:10.1001/jama.2019.3678