Fetal Alcohol Syndrome (FAS) is the most severe diagnosis within the Fetal Alcohol Spectrum Disorders (FASD), a group of conditions that occur in a person whose mother consumed alcohol during pregnancy. A diagnosis of FAS is highly specific and requires meeting four distinct criteria established by major medical and health organizations. The process involves a thorough, multi-disciplinary evaluation to confirm a characteristic pattern of physical, growth, and neurological abnormalities. Meeting all four criteria is necessary to ensure the diagnosis is precise and not mistaken for other conditions with similar symptoms.
Documenting Prenatal Alcohol Exposure
The first step in establishing a diagnosis is documenting the mother’s alcohol consumption during the pregnancy, which is referred to as prenatal alcohol exposure (PAE). While the diagnosis of FAS can sometimes be made even without confirmed PAE if the physical features are fully present, the most definitive diagnosis is made when exposure is known. Documentation relies on obtaining reliable reports of alcohol use, which can include the mother’s self-report, accounts from family members or other credible informants, or existing medical records.
The assessment aims to determine the quantity, frequency, and timing of alcohol use, as these factors influence the severity and type of damage. Heavy alcohol use, particularly binge drinking, is strongly associated with an increased risk of FAS. Clinicians must conduct this history-taking with sensitivity, as admitting to alcohol use during pregnancy can be difficult and stigmatizing. Confirmation of exposure helps distinguish FAS from other disorders that may cause similar features but have different underlying causes.
Specific Facial Characteristics
The second criterion focuses on the presence of a distinct pattern of three specific facial features, which are considered a hallmark of FAS. These dysmorphic features must all be present to meet this part of the diagnostic standard. The first feature is short palpebral fissures, which refers to the small horizontal length of the eye openings.
A second defining feature is a thin vermillion border, which describes a narrow or thin upper lip. The third characteristic is a smooth or flattened philtrum, which is the vertical groove or ridge located between the base of the nose and the upper lip. These three features—short palpebral fissures, thin upper lip, and smooth philtrum—are a unique cluster of physical changes caused by the teratogenic effects of alcohol on the developing face and brain.
These physical traits result from damage that occurs early in gestation, particularly during the first trimester when the facial structures are forming. Clinicians often use standardized visual guides, sometimes called a Lip-Philtrum Guide, to objectively score the philtrum’s smoothness and the upper lip’s thinness. The presence of all three facial features is the most visually defining and measurable component of the FAS diagnosis.
Measuring Growth Deficiencies
The third criterion for an FAS diagnosis involves documenting growth deficits, which can occur both before and after birth. This requires a quantitative measurement of the individual’s size against standardized growth charts adjusted for age and sex. Specifically, the individual must have a height or length, and/or weight, that measures at or below the 10th percentile.
This means that out of 100 children of the same age and sex, the child with FAS would be smaller than at least 90 of them. The deficit can be documented prenatally, such as low birth weight or length, or postnatally at the time of diagnosis.
The growth deficit is a direct consequence of prenatal alcohol exposure interfering with normal development, not poor nutrition after birth. Measurements are taken and plotted on standard charts. If height, length, or weight falls significantly low (at or below the 10th percentile), it provides strong evidence for meeting this criterion.
Identifying Central Nervous System Impairment
The final and most complex criterion requires evidence of clinically significant impairment in the central nervous system (CNS), which includes the brain and spinal cord. This impairment can be documented in three main categories: structural, neurological, or functional deficits.
Structural abnormalities refer to physical changes in the brain, such as microcephaly, where the head circumference is small, typically at or below the 10th percentile. Structural changes may also include specific alterations visible on brain imaging, like a reduction in the size or change in the shape of the corpus callosum, cerebellum, or basal ganglia.
Neurological problems involve signs of damage to the nervous system that affect movement and coordination. These can include issues like poor fine motor skills, tremors, visual-motor coordination difficulties, or problems with balance.
Functional or developmental deficits are often the most varied, affecting a person’s cognitive and behavioral abilities. These deficits can manifest as significant intellectual disability, attention deficits, poor executive functioning (involving planning, working memory, and impulse control), or severe behavioral problems. Evidence of CNS impairment must be substantial in one or more of these areas, often requiring extensive psychological and neurodevelopmental testing by a multidisciplinary team.