BACKGROUND: TennCare expanded Medicaid coverage, substituting managed care for fee-for-service reimbursement in Tennessee. METHODS: To study effects of TennCare on utilization of obstetric care (office visits, prenatal tests, care at labor/delivery), we used a before (1993) and after (1995) design with North Carolina as a control state. Data came from interviews with women with various forms of insurance, delivering in 1993 or 1995 in both states. Multivariate logistic analysis was used to control for other utilization determinants (eg, demographic factors). RESULTS: TennCare women were only 38% as likely to have initiated prenatal care during the first trimester as those with traditional Medicaid. Ultrasonography and alpha-fetoprotein testing rates were higher for TennCare women, and the cesarean section rate was equivalent. However, access to care remained lower for TennCare than for the privately insured women. CONCLUSIONS: Overall, relative to traditional Medicaid, TennCare did not adversely affect access to obstetric care during the program's early years.