Objective: To examine trends in prenatal insurance coverage and utilization of care in California over two decades in the context of expansions in Medi-Cal (California's Medicaid) and other public efforts to increase prenatal care utilization. Methods: Retrospective univariate and bivariate analysis of prenatal care coverage and utilization data from 10,192,165 California birth certificates, 1980–99; descriptive analysis of California poverty and unemployment data from the U.S. Census Bureau Current Population Survey; review of public health and social policy literature. Results: The proportion of mothers with Medi-Cal coverage for prenatal care increased from 28.2 to 47.5% between 1989 and 1994, and the proportion uninsured throughout pregnancy decreased from 13.2 to 3.2%. Since the mid-1990s, fewer than 3% of women have had no insurance coverage for prenatal care. Between 1989 and 1999, the proportion of women with first trimester initiation of prenatal care increased from 72.6 to 83.6%, reversing the previous decade's trend, and the proportion of women with adequate numbers of visits rose from 70.7 to 83.1%. Improvements in utilization measures were greater among disadvantaged social groups. Improvements in California during the 1990s coincided with a multifaceted public health effort to increase both prenatal care coverage and utilization, and do not appear to be explained by changes in the economy, maternal characteristics, the overall organization/delivery of health care, or other social policies. Conclusions: While this ecologic study cannot produce definitive conclusions regarding causality, these results suggest an important victory for public health in California.