This study investigated the relationship between social capital and social support and the adequate use of prenatal care. A follow-up study involving 1,485 pregnant women was conducted in two cities in the Rio de Janeiro State, Brazil. Demographic and socioeconomic characteristics, social support and social capital data were collected during the first trimester of pregnancy. The post-partum period included information on levels of prenatal care utilization, social networks, parity, obstetric and gestational risk and prenatal care attendance. Hierarchized multinomial logistic regression was used in the statistical analysis. Prenatal care use above adequate levels was associated with high social capital at the city level (aggregated social capital), socioeconomic status and working during pregnancy. Lower non-aggregated contextual and compositional social capital, gestational risk and pattern of prenatal care were associated with inadequate prenatal care utilization. Contextual social capital and social support were found to be social determinants for the appropriate use of prenatal care.