OBJECTIVE: To determine the association of maternal and prenatal WIC program participation characteristics with low prenatal weight gain among adult women delivering liveborn, singleton infants at term. METHODS: WIC program data for 19,017 Black and White Alabama women delivering in 1994 were linked with birth certificate files to examine the association of anthropometric, demographic, reproductive, hematologic, behavioral and program participation characteristics with low prenatal weight gain. RESULTS: One third (31.0%) had low prenatal weight gain as defined by the Institute of Medicine. The incidence of low weight gain was increased among women who had < 12 years of education, were single, Black, anemic, had low or normal prepregnancy body mass index (BMI), increased parity, interpregnancy intervals < or = 24 months, used tobacco or alcohol, or entered prenatal care or WIC programs after the first trimester. After adjusting for selected maternal characteristics, the adjusted odds ratios (AOR) for low weight gain were increased with short interpregnancy intervals (AOR 1.21 to 2.20); tobacco use (AOR 1.16 to 1.40), anemia (AOR 1.20 to 1.25), and second trimester entry into prenatal care (AOR 1.14 to 1.20); the size of the AORs and 95% confidence intervals varied by BMI and racial subgroup. CONCLUSIONS: The results of this study suggest that WIC interventions targeting low prenatal weight gain be focused on risk factors present not only during pregnancy, but during the pre- and interconceptional periods as well. Interventions should target low BMI, tobacco use, and anemia, and include attention to nutrition screening and risk reduction among women in postpartum and family planning clinic settings.