Medicaid, the state-federal health insurance program for individuals with low incomes, serves as a safety net for women throughout the life span. Historically, expansions of Medicaid have been associated with improved access to health care, less delay in obtaining health care, better self-reported health, and reductions in mortality. Compared with nonexpansion states, states that have participated in the Affordable Care Act's Medicaid expansion have experienced improvements in maternal and infant mortality and decreases in uninsured rates and have decreased racial inequities for these measures. In addition to supporting policies that expand access to Medicaid, the American College of Obstetricians and Gynecologists strongly supports education for its members, other obstetrician-gynecologists, and other health care practitioners regarding the complex system for regulation of Medicaid and encourages advocacy for policies that increase access to care for all women. This Committee Opinion has been revised to emphasize the importance of Medicaid to improving women's health, the history and growth of Medicaid, including the ACA's Medicaid expansion, and the mechanisms by which changes to the Medicaid program can occur, and it includes relevant examples for each.