Suspicion of alcohol's teratogenic potential stretches back many centuries, but it is only recently that solid support for this possibility has been produced. There is now little doubt that alcohol can produce developmental defects, but there are many questions that still remain to be answered concerning the impact of alcohol on the conceptus. One major question that remains to be resolved is why only a small percentage of alcoholic women give birth to children with Fetal Alcohol Syndrome (FAS), whereas other alcoholic women who drink the same amount do not. Another important issue concerns the way in which alcohol produces its effects. Although one of the most likely ways in which alcohol's teratogenic actions are mediated appears to be via hypoxia, other mechanisms such as direct toxicity of alcohol or acetaldehyde may be involved. FAS refers to a pattern of defects in children born to alcoholic women. For a diagnosis of FAS to be made, the patient must have three main characteristics: (1) pre- and postnatal growth retardation (greater than or equal to 2 S.D. for length and weight), (2) facial anomalies, and (3) central nervous system dysfunction Pre- and postnatal growth retardation are the most reliable consequences of fetal alcohol exposure. In many cases, patients with the syndrome weigh less than 2500 g at birth and most do not exhibit postnatal 'catch-up growth' Among the distinctive facial anomalies seen in conjunction with the syndrome are absent-to-indistinct philtrum, epicanthic folds, thin upper lip and short upturned nose. Joint, limb and cardiac anomalies are also often present. Central nervous system dysfunction includes mental retardation, the most serious consequence of in utero alcohol exposure, hyperactivity, sleep disorders and miscellaneous behavioral difficulties. If only one or two of these broad characteristics are present and the mother is suspected of drinking during pregnancy, then a diagnosis of 'possible fetal alcohol syndrome,' or 'partial fetal alcohol syndrome,' or 'fetal alcohol effects,' or 'alcohol-related birth defects' may be made. However, without evidence of maternal drinking during pregnancy, this diagnosis is very tentative, since many of these effects are also observed in conjunction with many other congenital disorders.(ABSTRACT TRUNCATED AT 400 WORDS)