Prenatal Insurance Coverage for Undocumented Immigrants Improves Birth Outcomes

Figure 1

Medicaid coverage for prenatal care has expanded considerably in recent decades. But in many states, undocumented immigrants remain ineligible for this coverage. This exclusion is consequential because one in thirteen births in the United States is to an undocumented immigrant. In Covering Undocumented Immigrants: The Effects of a Large-Scale Prenatal Care Intervention (NBER Working Paper 30299), researchers Sarah Miller and Laura Wherry evaluate the effects of California’s decision to expand prenatal Medicaid coverage to undocumented immigrants in October 1988.

At the time of the policy change, 25 percent of immigrant mothers in California reported no insurance coverage for prenatal care. They were less likely than US-born mothers to receive any prenatal care, and far less likely to initiate care during their first trimester of pregnancy.

The researchers analyze birth certificate records for all children born in California between 1984 and 1994 matched to survey data from the US Census Bureau. Their research design compares the differences in outcomes between those for expectant immigrant mothers, who may have been affected by the expansion, and those for expectant US-born mothers, who were not affected by it, in the years before and after the change. To ensure the comparability of mothers over the 10 year sample period, they focus their analysis on siblings who were born to the same mother before and after the expansion.

California’s policy change had enormous effects on Medicaid eligibility and coverage. The researchers estimate that 22 percent of pregnant immigrants gained Medicaid eligibility and 17 percent gained coverage. Uninsurance rates fell by a corresponding 15 percentage points, demonstrating that few of the affected immigrants would have obtained other coverage in the absence of the policy change.

The first figure illustrates a relative increase in prenatal care for pregnant immigrants after the expansion, with effects emerging immediately after the policy change and rising over time. Averaged across the first five years, the expansion generated a 1.1 percentage point increase in the likelihood that immigrant mothers received any prenatal care, nearly eliminating the prior disparity in rates of prenatal care use between immigrant and US-born mothers. The number of prenatal visits during a pregnancy rose by 0.75 (8 percent) for immigrants. In addition, the Medicaid expansion increased the likelihood of early prenatal care, delivery at a hospital, and delivery by a doctor.

Figure 2

The second figure demonstrates that these changes also improved average birth outcomes, with effects that increased over time. Infants born to immigrant mothers after the expansion had, on average, 0.62 days longer gestational age (0.2 percent) and 22 grams greater birthweight (1 percent).

While the average effects are relatively small, the implied effects on the newly covered immigrant women and their infants are much larger. Immigrant women who gained insurance coverage due to the policy change were 7 percentage points more likely to use any prenatal care, and used 4.5 more visits (47 percent) during their pregnancies. The children of newly covered immigrant mothers gained 130 grams in birthweight (4 percent) and 3.7 days of gestational age (1 percent).

The researchers point out the potential for long-term effects from this policy change. They write that, if health at early ages has long-run effects, “expanding prenatal Medicaid eligibility to undocumented immigrants may have a significant impact on the health and economic outcomes of the next generation of Americans.”

The researchers acknowledge support from the National Institute on Aging under grant R01-AG059731 and from the Laura and John Arnold Foundation. They also acknowledge non-financial support from the California Center for Population Research at UCLA, which receives core support (grant R24-HD041022) from the Eunice Kennedy Shriver National Institute of Child Health and Human Development.