Effect of Medicaid expansions on preterm birth

Inadequate prenatal care is thought to be a major modifiable risk factor for preterm birth, the leading cause of neonatal mortality. To improve high-risk women's financial access to prenatal care, the U.S. Medicaid program underwent major expansions during the 1980s. We evaluated these expansions over the nine-year period 1983 to 1991 in Tennessee to determine their effects on Medicaid enrollment, use of prenatal care, and preterm birth.

We used linked birth certificates, Medicaid data, and U.S. Census files to identify 610,056 singleton births to African-American or Caucasian women in Tennessee whose last menstrual period was between 1983 and 1991. These were classified by maternal characteristics to identify groups with the greatest postexpansion increases in Medicaid enrollment, which should have benefited most from the policy changes. Study outcomes were Medicaid enrollment by delivery, enrollment in the first trimester, inadequate prenatal care (modified Kessner index), and preterm (< 37 weeks) birth. We calculated the changes (delta expressed as births per 100) between 1983 and 1991 in percentages of births with each of these outcomes.

The expansions led to pronounced increases in maternal Medicaid enrollment by delivery (21% of births in 1983 to 51% by 1991) and in the first trimester (from 10% to 37%). Married women with < 12 years of education, < 25 years of age, and < $12,500 mean neighborhood incomes (group 1) had the greatest increase, where enrollment and first-trimester enrollment increased from 24% to 86% and 7% to 68%, respectively. In group 1, the percentages of births with inadequate maternal use of prenatal care decreased substantially, from 12.8% in 1983 to 6.4% in 1991, a reduction of 6.4 births per 100 (95% confidence intervals [CI] = -7.6, -5.3). However, the preterm birth rate did not decrease (9.1% in 1983, 9.4% in 1991, change of 0.3[-0.7 to 1.2] births per 100). For other births, there were lesser increases in Medicaid enrollment, correspondingly lesser decreases in inadequate use of prenatal care, but no reductions in preterm birth rates.

In Tennessee, the Medicaid expansions materially increased enrollment and use of prenatal care among high-risk women, but did not reduce the likelihood of preterm birth.