these elements diagnostically. The IOM and Canadian guidelines explore this further, acknowledging the importance of significant alcohol exposure from regular or heavy episodic alcohol consumption in determining, but offer no standard for diagnosis. 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. Biomarkers Evidence is insufficient for the use of chemical biomarkers to detect prenatal alcohol exposure. Biomarkers being studied include fatty acid ethyl esters (FAEE) detected in the meconium (first feces of an infant) and hair. FAEE may be present if chronic alcohol exposure occurs during the 2nd and 3rd trimester since this is when the meconium begins to form. Concentrations of FAEE can be influence by medication use, diet, and individual genetic variations in FAEE metabolism however. Ten brain domains A recent effort to standardize assessment of functional CNS damage has been suggested by an experienced FASD diagnostic team in Minnesota. The proposed framework attempts to harmonize IOM, 4-Digit Diagnostic Code, CDC, and Canadian guidelines for measuring CNS damage vis-à-vis