Transplacental carcinogens.

Cancer can metastasize to the placenta and to the fetus, and it may arise in man without familial predisposition in fetal or early postnatal life. Carcinogens administered to the mother can induce cancer in the human fetus and experimental animals. Many potential carcinogens tend to act as abortifacients and teratogens as well as carcinogens. Carcinogens administered to mothers can be dispersed by all their metabolic pathways and can be transferred transplacentally. In each exposed fetus, further metabolic pathways, or absence therof, as well as the individual gene makeup, influence the expression of an agent's potential. In the future, experimental evidence defining the pathways of carcinogenesis in adults will provide clearer insight into how cancers arise. This will be most helpful in unraveling the more complex issue of transplacental carcinogens.