ABSTRACT
The beliefs that pregnancy and early childhood are periods of particular susceptibility to the toxic effects of drugs and other chemical substances have long been held and probably have their origin in folklore. Teratogenesis, transplacental carcinogenesis, abortion, and infantile mortality may thus be the occasional tragic legacies of drug administration to infants or the results of incautious taking of drugs during pregnancy, the puerperium, or the postnatal period of lactation. Contraceptive estrogen-progestogen preparations may diminish lactation and ethynylestradiol can result in increased protein content of the milk. Breast milk sometimes is the causative agent of neonatal unconjugated hyperbilirubinemia, probably because of the presence of inhibitors of hepatic glucuronyl transferase. Most of the organophosphate insecticides are more toxic to weanling animals than to adults, the esterase enzyme system that is responsible for the detoxication of malathion and malaoxon being depressed or absent at birth like many other hepatic microsomal enzymes.
