TREATMENT OF LEAD POISONING IN PREGNANCY

Exposure to high concentrations of lead during pregnancy may result in adverse outcomes, including miscarriage, impaired intrauterine growth, premature rupture of the membranes and/or preterm labour, reduced infant head circumference, and impaired neurodevelopment in the child. However, these risks have not been clearly quantified.

It is important that the source of lead exposure is identified and the risk of further exposure minimised. Iron and calcium deficiency should be corrected.

Current National Poisons Information Service (NPIS) advice is that all adults with a blood lead concentration of ≥50 micrograms/dL (2.4 micromol/L) should be considered for chelation therapy. This includes women who are pregnant. There are very small numbers of published cases on which to base an assessment of the safety of chelating agents in pregnancy, with no data on first trimester use. However, because of the risks associated with severe maternal lead poisoning, the benefits of chelation are likely to outweigh any potential risks to the fetus. The NPIS currently advises chelation with either intravenous sodium calcium edetate 75mg/kg/day or oral DMSA (succimer) 30mg/kg/day in non-pregnant individuals with a blood lead concentration of ≥50 micrograms/dL (2.4 micromol/L). There is slightly more information on use of sodium calcium edetate in human pregnancy (seven case reports) in comparison with DMSA (two case reports, both involve use after the first trimester).

In theory, maternal chelation therapy may reduce fetal lead exposure and consequent adverse fetal effects, but there is also a theoretical risk that it could result in mobilisation of lead from the mother into fetal tissue and is therefore not routinely recommended where maternal blood lead concentration is <50 micrograms/dL (2.4 micromol/L). Available data indicate that maternal chelation therapy has a limited effect on the fetal blood lead concentration and additional neonatal chelation is often required.

UKTIS should be contacted directly to discuss the treatment of any pregnant patient, including those with blood lead concentrations of <50 micrograms/dL (2.4 micromol/L).

Exposure to lead chelating treatments at any stage in pregnancy would not usually be regarded as medical grounds for termination of pregnancy. Monitoring of fetal growth may be advisable following maternal exposure to lead. Other risk factors may also be present in individual cases which may independently increase the risk of adverse pregnancy outcome. Clinicians are reminded of the importance of consideration of such factors when performing case-specific risk assessments.