ABSTRACT
Congenital malformations have been observed for centuries without knowing their etiology. It was only early last century that a variety of malformations were reported among the offspring of mothers who had been exposed to radiation, nutritional deficiencies, or certain viral infections. A connection was not suspected to exist between congenital malformation and chemicals because there was a tendency among toxicologists to assume that the natural protective mechanisms, such as detoxication, elimination, and placental barrier, were sufficient to shield the embryo from maternal exposure to chemicals. On the other hand, it was not unexpected that the natural protective mechanisms were ineffective against ionizing radiation, viruses, and nutritional deficiencies.
