LEAD-POISONING IN PREGNANCY

Endemic areas of lead poisoning have recently been rediscovered raising an important public health problem, particularly for pregnant women and their offspring. Theoretically, pregnant women can no longer be exposed to occupational sources with the application of public health regulations but other sources including water contamination, wall paint, industrial wastes and automobile exhaust fumes cannot be ignored. The placental barrier is permeable to free serum lead and levels in cord blood reaches 5 to 10% of the maternal blood level. In addition, lead may be released from maternal bone reserves during pregnancy and thus become a major source of intoxication for the fetus. Lead content in fetal organs increases with gestational age and may affect the nervous system and calcium dependent organs. Moderate lead levels of 100 mu g/L can inhibit fetal haeme and erythropoiesis. Besides the classical signs of lead poisoning, pregnant women risk spontaneous abortion and increased blood pressure. Manifestations in the fetus and newborne include prematurity, fetal hypotrophy and malformations. Other manifestations are not seen until several years after birth and include retarded mental development and muscular and behaviour disorders. Diagnosis is based on screening tests,which should be used in cases of suspected accidental or environmental intoxication. Tests should include assay of zinc protoporphyrins and aminolevulinic acid dehydrase. A search for the source of the contamination should be undertaken when blood levels above 250 mu g/L are observed. Treatment with metal chelators is not recommendable (except in extreme life-threatening cases) during pregnancy due to their teratogenic effect. Prevention is the only adequate treatment.