A retrospective, observational study of 3073 low income African American, Latina, and White women receiving comprehensive prenatal care at 26 provider sites was completed. The purpose of the study was to test three hypotheses. First, after adjustment for biomedical complications, the presence of maternal behavioral and psychosocial factors would be associated with an increased rate of low birthweight infants. Second, increased time spent in psychosocial services would negate the relationship between maternal psychosocial factors and low birthweight. Third, after adjusting for biomedical, behavioral, and psychosocial factors, rates of low birthweight would no longer differ by race. Maternal smoking (over five cigarettes per week), maternal low weight for height and/or weight gain, negative mood (depression, anxiety, and/or hostility) and rejection of the pregnancy were found to be related to an increased rate of low birthweight birth (< 2500 g). Receiving more than 45 min of psychosocial services was related to a reduced rate of low birthweight birth for all women regardless of risk profile. The rate of low birthweight remained higher in African American women after adjusting for all significant maternal biomedical, behavioral, and psychosocial risk and intervention factors. Further analyses revealed that the strength and direction of the relationship between time spent in psychosocial services and low birthweight remained after controlling for the number of prenatal care visits, the time spent in nutrition or health educational services, and gestational age. Also, the time spent in psychosocial services was related to a reduced rate of low birthweight even after excluding time spent in psychosocial services in the third trimester of pregnancy or excluding women who received their first psychosocial assessment in the third trimester from the analysis. Although definitive evidence from randomized trials of psychosocial services is lacking, receiving over 45 min of psychosocial services was related to a reduced risk of low birthweight for all women in this study. Therefore, general psychosocial services appears to be an important component of prenatal care for all low income women.