Prenatal exposure to lead produces toxic effects in the human fetus, including an increased risk of preterm delivery, low birth weight and impaired mental development. Since we believe that placental lead could be a good biomarker for fetal exposure, we assessed the relation of placental lead to intrauterine fetal growth and some adverse outcomes of pregnancy. Low concentrations of lead were found in the population studied (N, 89; mean, 113.4 ng/g dry tissue; S.D., 58.0). The cases were divided into two groups based on delivery outcome. In the group of placentas from premature rupture of membranes and preterm labor (gestational age <or=37 weeks), higher lead levels were recorded than in the placentas from term pregnancies. The proportion of abnormal pregnancy outcome in the group of placentas with lead concentrations above 120 ng/g was 40.6 versus 8.8% in placentas below this concentration. Higher placental lead levels, in general, were not related to smaller weight, head and abdominal circumference or shorter length at birth.