We used data from a national serosurvey to describe national and regional trends in the prevalence of HIV among women giving birth in the United States from 1989 through 1994, and to estimate the number of women between 15 and 44 years old with HIV infection who had not yet developed opportunistic infections defining AIDS. We compared these estimates with AIDS prevalence and mortality estimates from the national AIDS case surveillance system. HIV seroprevalence among childbearing women remained stable nationwide from 1989 through 1994, ranging from 1.5 to 1.7/1000 women. In the Northeast, seroprevalence declined significantly after 1989. Seroprevalence increased significantly in the South through 1991 and then stabilized, although seroprevalence among black women continued to increase through 1994 in some southern states. Although AIDS prevalence and mortality increased nationwide each year from 1989 through 1994, the number of women infected with HIV who had not yet developed AIDS changed little and was approximately 86,000 in 1994. Our data suggest that new HIV infections among women of reproductive age are occurring at a rate that offsets losses from this population due to aging, disease progression, and death.