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.
Canadian guidelines discuss this lack of clarity and parenthetically point out that "heavy alcohol use" is defined by the National Institute on Alcohol Abuse and Alcoholism as five or more drinks per episode on five or more days during a 30-day period. "The 4-Digit Diagnostic Code" ranking system distinguishes between levels of prenatal alcohol exposure as high risk and some risk. It operationalizes high risk exposure as a blood alcohol concentration (BAC) greater than 100 mg/dL delivered at least weekly in early pregnancy. This BAC level is typically reached by a 55 kg female drinking six to eight beers in one sitting. Unknown exposure
For many adopted or adults and children in foster care, records or other reliable sources may not be available for review. Reporting alcohol use during pregnancy can also be stigmatizing to birth mothers, especially if alcohol use is ongoing. In these cases, all diagnostic systems use an unknown prenatal alcohol exposure designation. A diagnosis of FAS is still possible with an unknown exposure level if other key features of FASD are present at clinical levels. Confirmed absence of exposure
Confirmed absence of exposure would apply to planned pregnancies in which no alcohol was used or pregnancies of women who do not use alcohol or report no use during the pregnancy. This designation is relatively rare, as most people presenting for an FASD evaluation are at least suspected to have had a prenatal alcohol exposure due to presence of other key features of FASD.