Lead Poisoning and Chelation in a Mother-Neonate Pair

Abstract

We report the case of a pregnant woman with chronic lead toxicity and a blood lead of 57 microg/dL (2.7 micromol/L) who gave birth to a healthy-appearing neonate with a cord blood lead of 126 microg/dL (6.08 micromol/L). The mother was prescribed a single course of oral succimer late in the third trimester of pregnancy, without any appreciable change in her blood lead. The neonate was initially treated with intramuscular dimercaprol and intravenous edetate calcium disodium. After 3 days, the neonate was then switched to oral 2,3-dimercaptosuccinic acid because the blood lead had declined. The child received two 19-day courses of 2,3-dimercaptosuccinic acid and had a blood lead level of 21.5 microg/dL (1.04 micromol/L) at 5 months of age. Despite extensive investigation, the precise source of the mother's lead toxicity remained undetermined.

Dimercaptosuccinic acid (succimer; DMSA) in inorganic lead poisoning

“…79 For this reason sodium calcium edetate is generally preferred in pregnancy. 78 However, there is one case report of oral DMSA use in the treatment of maternal lead poisoning, 73,80 and five neonates have been treated with DMSA; 73,81-85 two of these were also given other chelation therapy. 73,82,85 A woman with chronic lead toxicity (blood lead concentrations 62.8 and 44.0 μg/dL at 25 and 29 weeks gestation, respectively) was treated with a single course of oral DMSA (30 mg/kg/day for 5 days then 20 mg/kg/day for 13 days) commencing in the 29th week of gestation.…”

“…78 However, there is one case report of oral DMSA use in the treatment of maternal lead poisoning, 73,80 and five neonates have been treated with DMSA; 73,81-85 two of these were also given other chelation therapy. 73,82,85 A woman with chronic lead toxicity (blood lead concentrations 62.8 and 44.0 μg/dL at 25 and 29 weeks gestation, respectively) was treated with a single course of oral DMSA (30 mg/kg/day for 5 days then 20 mg/kg/day for 13 days) commencing in the 29th week of gestation. 73,80 As DMSA had no impact on her blood lead concentration (pre-and postchelation concentrations were 44.0 and 43.9 μg/dL), issues of continuing exposure and compliance must be raised.…”

“…However, there are concerns that administration of chelation therapy to the mother during pregnancy may result in mobilization of lead from maternal to fetal tissues. 72,73 Balanced against this possible risk is that lead exposure during pregnancy may affect a child's physical development measured during the neonatal period and early childhood, 74,75 and that prenatal and postnatal lead exposure results in reduced intellectual development. 3,76 In fact, IQ decreased 1.8 points (95% CI, 1.0-2.6) for every doubling of prenatal blood lead, which was assessed as the average at mid-pregnancy and delivery.…”

“…73,82 Chelation therapy was commenced in the neonate 4 days post partum (blood lead concentration 74.7 μg/dL) with intramuscular dimercaprol 300 mg/m 2 /day and intravenous sodium calcium edetate 1,000 mg/m 2 /day for 3 days. After 24 h, oral DMSA 30 mg/kg/day was commenced and continued for 5 days then 20 mg/kg/day was given for 14 days.…”

“…73,82,85 A woman with chronic lead toxicity (blood lead concentrations 62.8 and 44.0 μg/dL at 25 and 29 weeks gestation, respectively) was treated with a single course of oral DMSA (30 mg/kg/day for 5 days then 20 mg/kg/day for 13 days) commencing in the 29th week of gestation. 73,80 As DMSA had no impact on her blood lead concentration (pre-and postchelation concentrations were 44.0 and 43.9 μg/dL), issues of continuing exposure and compliance must be raised. At parturition the mother's blood lead concentration was 57.6 μg/dL.…”