['To estimate the extent that prenatal care (PNC) retains its protective influence against prematurity, low birth weight (LBW), and small for gestational age (SGA) status in infants exposed to illicit drug use (IDU) in pregnancy.', 'This was a prospective cohort analysis including 6673 women residents of the District of Columbia (Washington, DC, USA) delivering at four city hospitals. Women were screened in the immediate postpartum period. Levels of PNC were established according to American College of Obstetrics and Gynecology guidelines and the Kotelchuck index. PNC and IDU were compared between subgroups. Adjusted relative risks for prematurity, LBW and SGA, controlling for maternal and gestational ages, were calculated in different groups according to IDU and level of PNC.', 'IDU was identified in 13% of mothers screened. PNC was classified as none (6%), inadequate (10%), intermediate (20%), and adequate (64%). The highest risk for prematurity, LBW, or SGA occurred in infants born to mothers with no PNC and positive IDU in pregnancy (prematurity OR=12.05, 95% CI: 8.99 to 16.16; LBW OR=14.76, 95% CI: 11.03 to 19.75; SGA OR=9.20, 95% CI: 5.32 to 15.92). As PNC levels increased, significant reductions in risk for prematurity and LBW (not for SGA) in IDU-exposed infants were observed. Risk for SGA in IDU-exposed infants reduced significantly when PNC was introduced.'] Does prenatal care reduce the impact of illicit drug use on perinatal outcomes?