The quantity and cost-effectiveness of prenatal care is a critical reproductive health issue as federal and state legislators consider reducing publicly funded services to aliens. An analysis of data from medi-Cal, California's Medicaid program, shows that undocumented and legalized aliens who qualified for coverage under the provisions of federal legislation or the state's expansion of eligibility criteria accounted for 45% of deliveries financed by Medi-Cal in 1991; outlays for these deliveries are estimated at less than 2% of all Medi-Cal payments for that year. Most of these women also received prenatal care covered by Medi-Cal, but more than half were not enrolled in the program until after the first trimester of pregnancy (and thus may not have received adequate prenatal care). Alien women were enrolled for an average of 5-6 months of their pregnancy, whereas nonalien women who qualified for coverage were enrolled for about seven months. California's Proposition 187 would eliminate funding for prenatal care for undocumented aliens, but public outlays for labor and delivery could grow as a result of an increase in poor birth outcomes.