In the past, any exposure to lead during pregnancy was thought to lead to miscarriages and premature births. However, one important thing to note is that the effects of lead are directly related to the levels of lead in the blood. Lead levels under 10 mcg/dl are thought to be safe and levels above 30 mcg/dL are associated with abnormalities in the infants of exposed mothers.
Placental transfer of lead has been studied along with the influence of other essential metals in its transfer. A recent study showed that maternal blood zinc and manganese decrease the placental transfer of lead. (1) This information has been used to encourage nutritional supplementation of these essential metals during pregnancy.
Studies of umbilical cord blood lead levels have shown that between 8.7 and 35.1 mcg/dL, infants were born with minor anomalies such as hydroceles, skin tags, and undescended testes. (2) However, there was no specific pattern which means the anomalies could have been caused by chance alone. At elevated levels, the incidence of neurotoxicity and developmental problems is also evident.
References:
1. Lin CM, Doyle P, Wang D, Hwang YH, Chen PC. The role of essential metals in the placental transfer of lead from mother to child. Reprod Toxicol. Mar 27.
2. Needleman HL, Rabinowitz M, Leviton A, Linn S, Schoenbaum S. The relationship between prenatal exposure to lead and congenital anomalies. JAMA. Jun 8 1984;251(22):2956-2959.
2. Needleman HL, Rabinowitz M, Leviton A, Linn S, Schoenbaum S. The relationship between prenatal exposure to lead and congenital anomalies. JAMA. Jun 8 1984;251(22):2956-2959.
