PROJECT SUMMARY State Medicaid programs pay for nearly half of all births in the United States (U.S.), financing over 1.6 million births in 2019. Federal law requires states to provide pregnancy-related Medicaid coverage to low-income pregnant individuals through 60 days postpartum, after which 1 in 4 become uninsured. A substantial and increasing proportion of adverse pregnancy-related outcomes, including maternal morbidity and mortality, are occurring among individuals with Medicaid-paid births and after pregnancy-related Medicaid coverage ends. Postpartum Medicaid eligibility extensions (PMEs) to one year postpartum are an emerging strategy for improving insurance enrollment, healthcare access, and health for low-income mothers and children. Passed in response to the COVID-19 Public Health Emergency, two federal laws have accelerated implementation of PMEs. First, the Families First Coronavirus Response Act (FFCRA) of March 2020 prevented states from disenrolling Medicaid beneficiaries during the public health emergency. In turn, the FFCRA created a national de facto PME. Second, the American Rescue Plan Act (ARPA) of March 2021 allows states to adopt PMEs starting in April 2022 with federal matching funds. Rigorous evaluations of these policies are urgently needed to inform state decisions to adopt PMEs and determine whether these polices are having the intended effect of improving maternal, child, and pregnancy-related health in the year after birth. To inform ongoing, evidence-based policymaking and fill this significant gap in maternal and child health research, our multi-disciplinary team will conduct rigorous, quasi-experimental evaluations that exploit state variation in policy adoption to provide timely data on the FFCRA and ARPA and associated changes in 1) maternal insurance enrollment, healthcare use, and health; 2) children’s insurance enrollment, healthcare use, and health; and 3) outcomes among subsequent pregnancies including rates of short interpregnancy interval and preterm births (NOT-HS-14-004). Given that a disproportionate share of those with Medicaid-paid births and experiencing adverse health events in the postpartum year are low-income and Black, Indigenous, or people of color (AHRQ priority populations), we will also measure the impact of PMEs on racial health equity (NOT-HS-21-014). The proposed set of evaluations will produce data directly informing whether these unprecedented, large-scale policy interventions have been associated with improvements in maternal and child health or racial and ethnic disparities in the year after birth. We will generate timely findings to inform ongoing, evidence-based policymaking to address the U.S. maternal health crisis. Ultimately, we aim to improve health and reduce disparities in the year after birth among low-income mothers and children at the population level.