Behavioral teratogenesis: an extension to the teratogenesis of functions.
Major malformations correspond to pathology during the first 2 months of gestation. Thereafter, histological and biochemical abnormalities can result from different negative maternal incidents and, without obvious malformations, change the phenotype of the conceptus. These abnormalities lead to essentially functional disorders often compatible with life and to more or less serious handicaps. All systems, when they arrive at such a stage of development, can be theoretically involved. The central nervous system (CNS) offers a very clear example of such weaknesses because its maturation is particularly long and susceptible to changes even after birth. The steps of this maturation overlap and form a continuum reflected in the pathology. Mental retardation occurring in children born of mothers who were subjected to atomic radiation, or ingested methylmercury from industrial waste, or who suffered the effects of lead, alcohol or tobacco constitutes a clear clinical example. Animal experiments confirm these data, adding pathogenic explanations. These experiments also explore the possible consequences that some medical techniques such as modern reproductive technology, for example embro freezing, can have on the development of the conceptus. Toxic substances or drugs can also be responsible for such abnormalities through a genetic attack on spermatogenesis. Behavioral teratogenesis also opens a larger perspective related to the optimal quality of the conceptus and the determining factors, from stress or dietary factors during apparently normal pregnancy to paternal age at the moment of conception. Finally, given that other systems than the CNS can be involved in histological or biochemical abnormalities, such as the reproductive system, we must ask what other types of functional pathology can be induced by interventions on gametes, the embryo and the fetus. Thus, behavioral teratogenesis leads to the teratogenesis of functions.