The current public health insurance landscape for postpartum women leaves many new mothers uninsured during the first year after pregnancy, because eligibility for pregnancy-related Medicaid/Children’s Health Insurance Program (CHIP) coverage ends 60 days after pregnancy ends. In this report, we assess how many uninsured new mothers would likely benefit from a 12-month postpartum Medicaid/CHIP extension. Using 2016–18 American Community Survey data and 2020 Medicaid/CHIP eligibility rules, we find that approximately 28 percent of the nation’s estimated 440,000 women uninsured during the first year postpartum, or 123,000 new mothers annually, would likely be newly eligible for Medicaid/CHIP if pregnancy-related coverage were extended for 12 months postpartum. An additional 27 percent of uninsured new mothers are likely already eligible for Medicaid but not enrolled, and 15 percent would likely be eligible for subsidized Marketplace coverage. Postpartum extension could help ensure many new mothers’ access to needed health care during the critical postpartum period.