The etiology of human malformations: Insights from epidemiology

Abstract

Abstract The epidemiological evidence that led to the incrimination of thalidomide as a teratogen was obtained by a combination of descriptive, correlative, analytic, and experimental studies. Most surveys of the common malformations have however been purely descriptive. Their main value has been to clarify the relative importance of the parts that genotype and environment in general play in causation. For example, it now seems that liability to neural tube defects is influenced much more by environment and less by genotype than is the case for cleft lip; that whether genetic or environmental, the influences that produce most cases of these and other common defects are multiple; and that if even one of these influences could be identified and controlled, incidence might fall substantially. The future for epidemiological research in this field seems to lie mainly in developing hypotheses about these influences from the knowledge already gained in descriptive studies, and in testing these hypotheses by correlative, analytic, and experimental methods.