Fetal alcohol syndrome (FAS): Diagnostic Criteria

by CDC

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For the majority of health-care providers, the key indicator of FAS is the set of characteristic facial features first described in 1973. Alcohol is a teratogen that results in dysmorphia, growth problems, and abnormalities of the central nervous system in multiple ways.

Confirmation and documentation of prenatal alcohol exposure can be difficult to establish. For birth mothers, admission of alcohol use during pregnancy can be stigmatizing. The situation can be further complicated if the woman continues to use alcohol, especially at high consumption rates. Clinicians might need to obtain information regarding alcohol use from other reliable informants, such as a relative.

Clinicians often have to evaluate a child or adult for FAS without definitive information regarding the mother's use of alcohol during pregnancy. This situation occurs frequently for children in foster and adoptive homes. In such cases, every effort should be made to obtain the necessary information, but lack of confirmation of alcohol use during pregnancy should not preclude a diagnosis of FAS if all other criteria are present. In rare instances, absence of exposure will be confirmed. Documentation that the birth mother did not drink any amount of alcohol from conception through birth would indicate that a FAS diagnosis is not appropriate. This finding typically implies either that the birth mother knew the date of conception (e.g., a planned pregnancy) and did not consume alcohol from that day forward or that she was prevented from drinking for a certain reason (e.g., incarceration).

Because of the imprecise nature of exposure information, the following two qualifying terms are suggested for a finding of prenatal alcohol exposure:

• FAS with confirmed prenatal alcohol exposure requires documentation of the alcohol consumption patterns of the birth mother during the index pregnancy on the basis of clinical observation; self-reports; reports of heavy alcohol use during pregnancy by a reliable informant; medical records documenting positive blood alcohol levels or alcohol treatment; or other social, legal, or medical problems related to drinking during the index pregnancy.

• FAS with unknown prenatal alcohol exposure indicates neither a confirmed presence nor a confirmed absence of exposure. Examples include situations in which the child is adopted, and any prenatal exposure is unknown; the birth mother is an alcoholic, but confirmed evidence of exposure during pregnancy does not exist; or conflicting reports regarding exposure exist that cannot be reliably resolved.

Prenatal exposure to alcohol alone is not sufficient to warrant a diagnosis of FAS. Despite the heterogeneity of expression for features related to prenatal exposure to alcohol, a diagnosis of FAS requires documentation of three findings: 1) three specific facial abnormalities; 2) growth deficit; and 3) CNS abnormalities (Appendix).

Considerations When Diagnosing FAS

Because FAS is a syndrome rather than a specific disease, additional features can be present. For example, in addition to the key facial dymorphic features, maxillary hypoplasia is often noted for persons with FAS. Features often change with age or development. After puberty, the characteristic facial features associated with FAS can become more difficult to detect. However, the key features remain constant for the majority of persons with FAS.

Changes in growth pattern across development also lead to variability in presentation. For certain affected persons, growth problems might occur at a younger age but not be present at the time of the diagnostic evaluation. This is particularly important when considering prenatal growth retardation or early growth problems caused by failure to thrive. Because multiple treatments exist for growth problems (e.g., use of feeding tubes or hormone therapy), any history of growth retardation, including prenatal growth deficiencies, is consistent with the criteria for diagnosing FAS. The clinician should be certain that the child was not nutritionally deprived at the single point in time when the growth deficit was present. The adopted threshold for growth (<10th percentile) represents an attempt to maximize sensitivity, even though it reduces specificity.

CNS Abnormalities

The diagnostic criteria for CNS abnormality require documentation of one of three types of deficits or abnormalities (i.e., structural, neurologic, and functional). A person might have more than one CNS abnormality. Identifying CNS abnormalities resulting from prenatal alcohol exposure can be the most difficult aspect of a FAS diagnosis because of the heterogeneity of expression for these deficits across persons (Appendix).

Approximately one fourth of persons who receive a diagnosis of FAS perform at two standard deviations below the mean (which approaches substantial impairment [i.e., mental retardation]) on standardized measures of cognition. To capture the full spectrum of effects adequately, two levels of functional deficits are consistent with the criteria for a CNS abnormality: 1) performance below the third percentile (i.e., two standard deviations below the mean) on a measure of global cognitive functioning or 2) performance < 16th percentile (i.e., one standard deviation below the mean) on standardized measures of three functional domains. Thus, persons scoring below the normal range on a global measure of intelligence or development and persons scoring in the below-average range on standardized measures of three specific functional domains would be consistent with the criteria for functional CNS abnormality for diagnostic purposes.

Because of the importance of documenting CNS abnormalities and the variability in functional deficits, the diagnostic process should include a thorough neuropsychologic evaluation that assesses multiple domains. Extensive standardized testing might not be readily available in all diagnostic settings. Clinicians are encouraged to supplement their observations by obtaining standardized testing through early intervention programs, public schools, and psychologists in private practice. Such testing will facilitate the development of appropriate personalized treatment plans for persons who receive a diagnosis of FAS. These guidelines recommend that functional domains be assessed by using norm-referenced standardized measures. Assessments should be conducted by professionals using reliable and validated instruments.

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