When a state expands Medicaid, does coverage always extend to low-income pregnant women? This Harvard Medical School study sought to measure whether Massachusetts' Healthy Start Program, a statewide perinatal program to provide health care to pregnant women with family incomes from 185% of poverty (the Medicaid eligibility cut-off) to 200% of poverty, reduced preventable morbidity and mortality by comparing hospital data from 1984 (one year before Healthy Start's initiation) and 1987 (two years after initiation). By simulating the effects of replicating a similar program in other states, the study is expected to help states evaluate the potential outcomes of expanding their Medicaid programs.