Insurance coverage

Prenatal insurance coverage for undocumented immigrants improves birth outcomes

Figure 1

Medicaid coverage for prenatal care has expanded dramatically over the past few decades. But in many states, undocumented immigrants remain ineligible for this coverage. This exclusion is significant 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 assess the effects of California’s decision to extend prenatal Medicaid coverage to undocumented immigrants in October 1988.

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

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

California’s policy change had huge effects on Medicaid eligibility and coverage. Researchers estimate that 22% of pregnant immigrants obtained Medicaid eligibility and 17% obtained coverage. Uninsured rates fell by a corresponding 15 percentage points, demonstrating that few affected immigrants would have obtained other coverage in the absence of the policy change.

The first figure illustrates a relative increase in antenatal care for pregnant immigrants after the expansion, with effects appearing immediately after the policy change and increasing over time. On average over the first five years, the expansion generated a 1.1 percentage point increase in the likelihood that immigrant mothers would receive prenatal care, nearly eliminating the previous disparity in prenatal care utilization rates among mothers immigrants and born in the United States. The number of prenatal visits during pregnancy increased by 0.75 (8%) for immigrants. Additionally, the expansion of Medicaid increased the likelihood of early prenatal care, delivery in a hospital, and delivery by a physician.

Figure 2

The second figure shows that these changes also improved mean birth outcomes, with effects increasing over time. Infants born to immigrant mothers after the expansion had, on average, a longer gestational age of 0.62 days (0.2%) and a higher birth weight of 22 grams (1%).

Although the average effects are relatively small, the implicit effects on newly covered immigrant women and their children are much larger. Immigrant women who obtained insurance coverage due to the policy change were 7 percentage points more likely to use prenatal care and used 4.5 more visits (47%) during their pregnancies. Children of newly covered immigrant mothers gained 130 grams of birth weight (4%) and 3.7 days of gestational age (1%).

The researchers point to the potential for long-term effects of this policy change. They write that, while health at an early age has long-term effects, “expanding prenatal Medicaid eligibility to undocumented immigrants can 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 the Laura and John Arnold Foundation. They also acknowledge in-kind 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.