Background. The influence of psychosocial factors such as stress, anxiety, depression, and self-esteem on birth weight is controversial. A prospective study was conducted to evaluate the relationship between pregnancy outcomes, psychosocial profile, and maternal health practices. Methods. 3,149 low-income, predominantly African-American pregnant women participated in this study. A 28-item psychosocial scale measured the constructs of negative and positive affect, self esteem, mastery, worry, and stress. Maternal health practices were assessed with 11 questions dealing with diet, exercise, and the use of preventive medical and dental services. Results. A low score on either scale indicated "poor" psychosocial or health practices status. Low birth weight, preterm delivery, and intrauterine growth retardation occurred in 10.9, 10.1 and 7.3% of the pregnant women respectively. In women with low psychosocial scores, the risk of both low birth weight and preterm delivery was 40% higher and the mean birth weight of infants was 51 g ( p =0.02) lower as compared to women with high scores. Negative affect (a measure of depression) was the only factor significantly associated with both infant birth weight (β = - 71.2, p =0.001) and low birth weight (AOR = 1.4, 95% CI = 1.1-1.7). When data were stratified by body mass index, the adverse effect of negative affect scores on birth weight and low birth weight was present only in thin women. Health practice scores were not associated with any of the pregnancy outcomes. Conclusion. Thin women with a poor psychosocial profile and who are depressed during pregnancy are at increased risk of giving birth to low birth weight and preterm infants. © 2006 Taylor & Francis.