This paper presents findings from a case study of Ohio's implementation of Medicaid managed care for pregnant women. Ohio Medicaid first implemented mandatory HMO enrollment in Montgomery County in the late l980s, and began offering voluntary enrollment in several other counties. Under the OhioCare waiver, six more counties began mandatory enrollment in the mid-1990s. Despite some early turmoil, the state developed strong guidelines for plans, both in terms of quality monitoring, the minimum number of enrollees in a county that the plan must have to participate, and other guidelines. As a result, Ohio's managed care model appears to benefit many pregnant women, once they are identified to health plans. However, since pregnant women often enroll late in their pregnancy--and lose eligibility between pregnancies--there is a limit to the overall impact that such a program can have on the health of Medicaid women.