Prenatal Exposure and Carcinogenesis

Abstract

There is epidemiological and experimental evidence which suggests that some neoplasms might have their origin during intrauterine life or before conception: the occurrence of cancer at birth or during the 1st mo. of life; age-distribution curves which show sharp peaks before 5 yr of age [acute lymphocytic leukemia, neuroblastoma, Wilm''s tumor, carcinoma of the liver, retinoblastoma, rhabdomyosarcoma, presacral teratoma and ependymoma]; the association between cancer and congenital malformations. At least 29 chemicals have been shown to induce tumors transplacentally in various experimental animals. Among these there are well known carcinogens such as benzopyrene, methylcholanthrene, urethane, nitrosamines and aflatoxin B. The critical factor which determines the ability of a chemical to produce tumors [as opposed to an embryotoxic effect] following prenatal exposure is the timing of its administration during pregnancy. Evidence of transplacental carcinogenesis in humans is discussed. Prenatal exposures to 3 different types of agents, which are associated with a high cancer risk for the progeny, have been reported in humans: diagnostic radiation, stilbestrol administration to pregnant women and viral infections such as influenza and chickenpox. Prezygotic determinants of childhood cancer are discussed. Experimental evidence suggests that the increased risk for cancer associated with prenatal exposures to a carcinogen persists for at least 2 generations.