Preconception and interconception health care are critical means of identifying, managing, and treating risk factors originating before pregnancy that can harm fetal development and maternal health. However, many women in the U.S. lack health insurance, limiting their ability to access such care. State-level variation in Medicaid eligibility, particularly before and after the 2014 Medicaid expansions, offers a unique opportunity to test the hypothesis that increasing healthcare coverage for low-income women can improve preconception and interconception healthcare access and utilization, chronic disease management, overall health, and health behaviors.