Up to term, fetal tissues do not have significant capacity for the detoxification of ethanol, and the fetus remains exposed to ethanol in the amniotic fluid for periods far longer than the decay time of ethanol in the maternal circulation. The lack of significant quantities of ADH and ALDH means that fetal tissues have much lower quantities of antioxidant enzymes, like SOD, glutathione transferases, and glutathion peroxidases, resulting in antioxidant protection being much less effective.Additionally, ethanol may alter fetal development by interfering with retinoic acid signaling. Acetaldehyde, the main ethanol metabolite, can compete with retinaldehyde and prevent its oxidation to retinoic acid. Diagnosis
Because admission of alcohol use during pregnancy can stigmatize birth mothers, many are reluctant to admit to drinking or to provide an accurate report of the quantity they drank. This complicates diagnosis and treatment of the syndrome. As a result, diagnosis of the severity of FASD relies on protocols of observation of the childs physiology and behavior rather than maternal self-reporting.
Most individuals with deficits resulting from prenatal alcohol exposure do not express all features of FAS and fall into other FASD conditions. The Canadian guidelines recommend the assessment and descriptive approach of the "4-Digit Diagnostic Code" for each key feature of FASD and the terminology of the IOM in diagnostic categories, excepting ARBD.Thus, other FASD conditions are partial expressions of FAS. However, these other FASD conditions may create disabilities similar to FAS if the key area of central nervous system damage shows clinical deficits in two or more of ten domains of brain functioning. Essentially, even though growth deficiency and/or FAS facial features may be mild or nonexistent in other FASD conditions, yet clinically significant brain damage of the central nervous system is present. In these other FASD conditions, an individual may be at greater risk for adverse outcomes because brain damage is present without associated visual cues of poor growth or the "FAS face" that might ordinarily trigger an FASD evaluation. Such individuals may be misdiagnosed with primary mental health disorders such as ADHD or oppositional defiance disorder without appreciation that brain damage is the underlying cause of these disorders, which requires a different treatment paradigm than typical mental health disorders. While other FASD conditions may not yet be included as an ICD or DSM-IV-TR diagnosis, they nonetheless pose significant impairment in functional behavior because of underlying brain damage.