This study aims to determine whether variables reflecting an adverse intrauterine environment are associated with childhood blood pressure. The authors conducted a secondary analysis of data from a prospective cohort of children born to healthy, nulliparous women enrolled in a randomized controlled trial. A total of 518 children were traced in 1995-1996 from 614 eligible children born in a clinic in Rosario, Argentina. The outcome was systolic blood pressure at 5-9 years. Hemoglobin during pregnancy was positively associated with children's pressure. Other maternal characteristics during pregnancy (blood pressure, smoking, weight gain, weight at 20 weeks' gestation, and glycemia) and size at birth (birth weight, ponderal index, head circumference/length ratio, and small for gestational age) were not associated with children's pressure. Among children in the upper quartile of body mass index, there was a weak inverse correlation between birth weight and systolic pressure, and systolic pressure was 14.8 mmHg (95 percent confidence interval: 3.3, 26.4) higher in low birth weight children than in others. The main predictors of childhood pressure were childhood body mass index and maternal pressure outside pregnancy. In this healthy population, the authors found weak support for an association between variables reflecting an adverse fetal environment and childhood blood pressure. Low birth weight was a risk factor for high blood pressure only in overweight children.