The research on expansions of Medicaid, both through the ACA and through earlier state expansions, is extensive and focuses on both a number of specific subgroups and on the overall population. To focus on the impact during the prenatal-to-3 period, the review of access and health outcomes presented here is limited to those outcomes relevant to the perinatal period, including perinatal insurance coverage and birth outcomes, and to those studies that focus on women who are of reproductive age or pregnant. Because of the significant impact of poverty on outcomes in early childhood,11 this review also considers the impact of state expansions of Medicaid on economic security outcomes, though most of these studies have broader samples than just parents of young children. A comprehensive literature review of all studies related to the passage of the ACA is available online through other sources.12
The research discussed here meets our standards of evidence for being methodologically strong and allowing for causal inference, unless otherwise noted. Each strong causal study reviewed has been assigned a letter, and a complete list of causal studies can be found at the end of this review, along with more details about our standards of evidence and review method. The findings from each strong causal study reviewed align with one of our eight policy goals from Table 1. The Evidence of Effectiveness table below displays the findings associated with state expansions of Medicaid (beneficial, null,vii or detrimental) for each of the strong studies (A through W) in the causal studies reference list, as well as our conclusions about the overall impact on each studied policy goal. The assessment of the overall impact for each studied policy goal weighs the timing of publication and relative strength of each study, as well as the size and direction of all measured indicators.
Table 3: Evidence of Effectiveness for Medicaid Expansion by Policy Goal
|Policy Goal||Indicator||Beneficial Impacts||Null Impacts||Detrimental Impacts||Overall Impact on Goal|
|Access to Needed Services||Perinatal Medicaid Coverage||B, E, D||Mostly Positive|
|Overall Perinatal Uninsurance Rates||C, H||B, E|
|Postpartum Medicaid Coverage||I|
|Receipt of Recommended Prenatal Screenings||D|
|Early Prenatal Care Use||E|
|Postpartum Outpatient Care Use||I|
|Primary Care Use||C|
|Sufficient Household Resources||Any Out-of-Pocket Spending on Health||F, G, M, Q||Positive|
|Real Health Spending||S|
|Medical Debt||F, G, R||N|
|New Medical Collections||N|
|Catastrophic Medical Expenditures||F|
|Problems Paying Medical Bills||K, L|
|Cost Barriers to Care||C, K, H|
|Number of Loans||O|
|Total Housing/Food Spending||S|
|Healthy and Equitable Births||Preterm Birth||A*||E||Mixed|
|Maternal Mortality Ratio||J|
|Parental Health and Emotional Wellbeing||Prenatal Vitamin Use||D||Mixed|
|Clinical Health Outcomes||F|
|Self-Reported Health||G||K, L|
|Blood Pressure Medication Use||H|
|Diagnosis of Chronic Disease||H|
|Mental Distress||L||H, K|
|Worry About Paying Medical Bills||K|
|Optimal Child Health and Development||Neglect Rates||U||Trending^ Positive|
|Physical Abuse Rates||U|
*Beneficial for reducing racial disparities, null for overall population
^Trending indicates that the evidence is from fewer than two strong causal studies or multiple studies that include only one location, author, or data set.
Access to Needed Services
The link between state Medicaid expansion and access to, and use of, preconception and interconception care through greater insurance coverage is key to the theoretical connection between Medicaid expansion and improved birth outcomes and health during the perinatal period. For the scope of the current review, this link is only examined for women of reproductive age, and evidence shows mostly positive impacts on perinatal insurance coverage and mixed impacts on health care use.
One multistate quasi-experimental study of preconception insurance coverage found an 8.6 percentage point increase in Medicaid coverage in expansion states, though the rates of overall uninsurance did not change, indicating that some individuals switched from private insurance to Medicaid coverage when they became eligible.B The same authors also conducted a national analysis with a sample of over 18 million and similarly found a 2.3 percentage point increase in Medicaid coverage during pregnancy but no significant impact on overall uninsurance rates during pregnancy.E Two quasi-experimental studies of women of reproductive age found beneficial impacts on overall insurance coverage in Medicaid expansion states, ranging from a 9 percentage point increase in the odds of being insuredH to a 13.2 percentage point decrease in overall uninsurance rates.C Finally, two studies of Medicaid expansion in Colorado and Ohio showed an average of 0.9 more months of Medicaid coverage postpartumI and an 11.75 percentage point increase in Medicaid enrollment prepregnancy for first-time mothers,D respectively.
Impacts of state Medicaid expansion on health care use among women of reproductive age are less conclusive. Rates of recommended prenatal screenings were 8.4 percentage points higher among first-time mothers (5.1 percentage points higher for all other mothers) after Ohio’s Medicaid expansion.D A quasi-experimental study of Colorado’s expansion similarly found a 17 percent increase in the number of outpatient visits postpartum.I However, two national studies showed no significant impacts on primary care useC or early prenatal care useE among women of reproductive age.
Sufficient Household Resources
Overall, state expansions of Medicaid have been shown to have beneficial impacts on economic security outcomes, especially those related to spending on health care. Two studies of the randomized Oregon Medicaid lottery found that the lottery reduced the likelihood of having any out-of-pocket medical spending by 15.3 to 20 percentage points, reduced the likelihood of having any outstanding medical debt collections by 6.4 to 13.3 percentage points, and reduced the incidence of catastrophic medical expenditures by 4.5 percentage points.G,F Similarly, a longitudinal treatment-on-the-treated study of enrollees after the ACA Medicaid expansion in Michigan found that enrolling in Medicaid was associated with a $563 reduction in medical debt.R A study of California’s early state Medicaid expansion also found a 10.1 percentage point decrease in any out-of-pocket medical spending for those with incomes below 200 percent of the FPL.Q Although these four studies each focus on a single geographic location, research using nationally representative data supports their findings. A 2020 study found that Medicaid expansion led to a 4.6 to 8.0 percentage point increase in the likelihood of having zero out-of-pocket expenditures for both insurance premiums and nonpremium medical spending, respectively.M Additionally, two national quasi-experimental studies found that Medicaid expansion decreased problems paying medical bills by 7.1 to 13.6 percentage points.K,L Another study with a sample of over 23 million records found a beneficial 3.3 percent reduction in the probability of having new medical bills sent to collections and a statistically insignificant beneficial impact on medical debt balances after state Medicaid expansion through the ACA.N
Evidence also shows a beneficial impact of Medicaid expansion on the avoidance of health care due to cost barriers. One national study of parents and women of reproductive age found a 3.8 percentage point reduction in cost barriers to care.C This finding is consistent with another national study that found a 7.4 percentage point reduction in avoiding care because of cost in the overall sample of women of reproductive age, with a larger 10.5 percentage point reduction among childless women.H A study of the longer-term impacts of Medicaid expansion similarly found a 3.8 to 5.6 percentage point decrease in delaying needed care due to cost, with the size of the effect growing over time, leading to a widening of the gap between expansion and nonexpansion states.K
Research has also shown that state expansions of Medicaid can impact nonmedical financial outcomes, though the findings are more mixed. One study found a small but statistically significant 0.1 percent increase in credit scores after Medicaid expansion,N and the study of Michigan’s Medicaid expansion through the ACA found an average reduction of $763 per person in total debt sent to collections over the two-year study period.R Another study of California’s early Medicaid expansion showed an 11 percent decrease in the number of loans and a 10 percent decrease in the amount borrowed from payday storefronts after the expansion.O However, one study of Oregon’s randomized Medicaid lottery found no significant association with nonmedical debt or nonmedical financial strain outcomes captured in administrative data.G
State expansions of Medicaid also have been shown to improve material wellbeing outcomes. A study of California’s early Medicaid expansion found 24.5 fewer evictions per month in the state overall after expansion, with the effect growing to 51.5 fewer evictions in counties with higher proportions of uninsured residents prior to the ACA.P The authors of this study also conducted a county-level analysis of nationwide evictions using Princeton Eviction Lab records and found 1.2 fewer evictions and 1.7 fewer eviction filings per 1,000 renters.T Another national quasi-experimental study found no statistically significant impact of Medicaid expansion on total household spending on housing or food.S
Healthy and Equitable Births
Evidence shows that although state expansions of Medicaid are not significantly associated with improved birth outcomes in the overall population, Medicaid expansions help to reduce racial disparities in preterm birth and infant mortality and to reduce both overall rates of, and racial disparities in, maternal mortality. Two quasi-experimental studies with samples of over one million births, one national and one focusing on a subset of states, found no significant differences in preterm birth, average birthweight, or infant mortality in expansion states relative to nonexpansion states.E,W Two additional quasi-experimental studies similarly found a null effect on birth outcomes for the overall sample but significant impacts for some racial groups when the sample was disaggregated. One study found that state Medicaid expansion was significantly associated with a 0.1 percentage point reduction in the incidence of very low birthweight and a 0.4 percentage point reduction in preterm birth rates among non-Hispanic Black infants compared to White infants in expansion states,A and the second study found 52.6 fewer infant deaths per 1000 live births among Hispanic infants in Medicaid expansion states compared to Hispanic infants in nonexpansion states.V A 2020 quasi-experimental study also found that Medicaid expansion was associated with 6.7 fewer maternal deaths overall per 100,000 live births; when disaggregated by race, the findings showed 16.3 fewer deaths among Black mothers, 6 fewer deaths among Hispanic mothers, and no significant impacts among White mothers.J
Parental Health and Emotional Wellbeing
Evidence shows that state expansions of Medicaid have mixed impacts on physical health outcomes relevant to the perinatal period. A quasi-experimental study of Ohio’s expansion found a 4.1 to 13.6 percentage point increase in use of prenatal vitamins, with effects larger among first-time mothers.D Similarly, a study of women of reproductive age found that Medicaid expansion was associated with a 7.9 percentage point increase in the use of blood pressure medicine and an 11.4 percentage point increase in the use of insulin.H Given the role of high blood pressure and gestational diabetes in birth outcomes and rates of maternal mortality and morbidity, these impacts are especially important during the perinatal period. However, the same study found no significant impact of Medicaid expansion on the diagnosis of chronic disease or likelihood of certain health behaviors, such as smoking or drinking. Further, evidence from the Oregon Medicaid lottery found no significant impact on clinical health outcomes,F and two quasi-experimental studies also found null impacts on self-reported health.K,L
Findings on the relationship between state expansions of Medicaid and mental health are also mixed. Whereas one study of low-income parents found a 10.9 percentage point reduction in retrospective self-reported severe psychological distress in expansion states relative to nonexpansion states,L another study with a large sample of women of reproductive age found no significant impact.H A study of the longer-term impacts of Medicaid expansion similarly found no significant impact on depression overall, though the study did find a 9.6 percentage point reduction in worrying about the ability to pay medical bills.K
Optimal Child Health and Development
Little research has been conducted on the relationship between Medicaid expansion and child health and development; only one study on child maltreatment rates meets our standards of strong causal evidence. The national study using state administrative data found that Medicaid expansion was associated with 422 fewer reported cases of neglect per 100,000 children under the age of six, but no significant association was found with rates of reported physical abuse.U Because neglect is often related to material wellbeing and medical care, it makes sense theoretically that Medicaid expansion should be more closely connected to neglect than child physical abuse.
- An impact is considered statistically significant if p<0.05.