Fetal alcohol syndrome: overview of pathogenesis.

The pathogenesis of Fetal Alcohol Syndrome (FAS) has been reviewed briefly in terms of factors which can influence its development and specific mechanisms. FAS was defined arbitrarily to include a wide spectrum ranging from the fully expressed clinical syndrome to growth and developmental impairment seen in fetal and neonatal animals exposed to ethanol. The available evidence suggests that ethanol per se in the absence of nutritional deficit can cause some from of FAS. Acetaldehyde may contribute to the FAS, but there is lack of knowledge concerning the levels of acetaldehyde needed to achieve fetal damage and the effect of this agent on the placenta and its placental transfer to the fetal organs. There is no specific data at this time to incriminate nutritional impairment, although further studies in animal models and man of the role of possible deficiencies of certain vitamins (i.e., folate) and of trace minerals (i.e., zinc) are needed. There is some evidence that alcohol or its metabolites may alter placental transport function. The relevance of this to FAS needs further investigation. The possible additive roles of caffeine, nicotine and other drugs on fetal development and viability deserve more consideration. The specific mechanism(s) of FAS are unknown. Of those considered--mutagenic (paternal) effect, abnormal protein synthesis, altered cerebral neurotransmitter balance, hormonal and other effects--impairment of protein synthesis at present seems best documented, but all clearly require further evaluation. When specific mechanisms are investigated it will be essential also to determine the dose-response relationship and the effects of a given dose of alcohol at various stages of gestation.