The role of essential metals in the placental transfer of lead from mother to child.

Epidemiological studies have found adverse birth and child health outcomes from prenatal lead exposure, but little is known about factors influencing placental transfer. In this study we describe the placental transfer of lead in a Taiwanese population, and investigate whether three essential metals - zinc, manganese, or selenium - influence transfer. Maternal and cord blood samples (308 pairs) from a birth cohort study were analyzed using multiple linear regression. There was a clear correlation between mother and child lead concentration (r=0.48, p<0.001), although lead concentration in cord blood (mean=1.29, SD=0.72 microg/dL) was lower than that for mothers (mean=1.58, SD=1.11 microg/dL). Cord blood lead was lower where the mother had a higher blood concentration of zinc (p<0.001) or manganese (p=0.02). Thus maternal blood zinc and manganese, but not selenium, appeared to decrease the placental transfer of lead. These findings raise the possibility of reducing placental transfer of lead by increasing zinc levels via nutritional supplementation during pregnancy.