Lead in the placenta, membranes, and umbilical cord in relation to pregnancy outcome in a lead-smelter community.

As part of a cohort study of the effects of chronic exposure to lead on pregnancy outcome and child development, lead concentrations in the umbilical cord and placental tissues (body and membranes) from 9 late fetal deaths, 23 preterm births, and 18 births associated with premature rupture of the amniotic membranes were compared with the lead concentrations in the tissues obtained at 22 normal births. Modest elevations in lead concentration were found in the placental body of late fetal deaths (stillbirths) and preterm births as well as in the cord tissue associated with preterm births and premature rupture of membranes. The geometric mean lead concentration in the membranes from late fetal deaths was 2.73 micrograms/g of dry tissue (95% confidence limits 0.69-10.8), which was 3.5 times higher than the mean found in normal births (0.78 micrograms/g, 95% confidence limits 0.61-1.00). The concentration in the membranes of preterm births was also significantly high, being 1.24 micrograms/G (0.91-1.67). Low correlations of membrane and antenatal blood lead concentrations suggest that other factors in addition to exposure to environmental lead may influence the amount of lead accumulated in the placental membranes.