What is fetal alcohol syndrome (FAS) in pediatric or adult patients exposed to alcohol in utero?

What is Fetal Alcohol Syndrome?

Fetal alcohol syndrome (FAS) is a lifelong condition resulting from maternal alcohol consumption during pregnancy, characterized by three essential diagnostic features: specific facial abnormalities (short palpebral fissures, smooth philtrum, thin upper lip), growth deficiency, and central nervous system dysfunction. 1

Core Diagnostic Criteria

FAS diagnosis requires all three of the following components to be present: 1

1. Characteristic Facial Features

• Short palpebral fissures (≤10th percentile) 1
• Smooth philtrum (the groove between nose and upper lip) 1
• Thin vermillion border of the upper lip 1

These three facial features are the key clinical indicators that distinguish FAS from other conditions and were first described in 1973. 1

2. Growth Deficiency

• Height and/or weight ≤10th percentile (not the more stringent 3rd percentile used for general growth retardation) 1
• This can be prenatal or postnatal growth restriction 1

3. Central Nervous System Abnormalities

Two levels of CNS dysfunction qualify for diagnosis: 1

• Structural abnormalities: Microcephaly (head circumference ≤10th percentile) or other documented brain malformations 1
• Functional deficits: Either global cognitive impairment (≥1.5 standard deviations below the mean on IQ testing) OR deficits ≥1 standard deviation below the mean in three or more functional domains including executive functioning, memory, attention, language processing, visual-spatial abilities, or behavioral regulation 1

The Broader Spectrum

FAS represents only the most severe end of a continuum called Fetal Alcohol Spectrum Disorders (FASD), which encompasses all effects from prenatal alcohol exposure including physical, mental, behavioral, and learning disabilities. 1 However, FASD is not a diagnostic category itself—it is an umbrella term. 1

Other conditions under FASD include alcohol-related neurodevelopmental disorder (ARND) and alcohol-related birth defects (ARBD), though diagnostic criteria for these remain less well-established than for FAS. 1

Critical Clinical Context

Prenatal Alcohol Exposure Documentation

• Confirmed maternal alcohol use during pregnancy strengthens the diagnosis but is not required if all three clinical criteria are met 1
• This is particularly important for adopted or foster children where maternal history is unavailable 1
• Lack of exposure confirmation should not prevent diagnosis when clinical features are present 1

Lifelong Consequences

The effects of FAS are permanent and lifelong, regardless of when diagnosis occurs: 1

• Intellectual disability and developmental delays 1
• Secondary disabilities including disrupted school experience, legal troubles, inappropriate sexual behaviors, and substance abuse problems 2
• Mental health comorbidities: conduct disorders, oppositional defiant disorder, anxiety, depression, and sleep disorders 1
• Adaptive functioning deficits affecting independent living, employment, and daily life skills 1

Differential Diagnosis Considerations

FAS must be distinguished from other conditions with overlapping features: 1

• Cornelia de Lange Syndrome: Has almond-shaped (not short) palpebral fissures, synophrys (eyebrows meeting in midline), and limb anomalies 3
• Williams Syndrome, Dubowitz Syndrome, Velocardiofacial Syndrome: Share some facial or growth features but lack the complete FAS constellation 1
• Toluene embryopathy: The only other syndrome with similar facial triad, but exposure history differs 1

Prevalence and Prevention

• FAS affects an estimated 1,000-6,000 infants born annually in the U.S., with rates of 0.5-2 per 1,000 live births 1
• Approximately 12-13% of U.S. women of childbearing age are at risk for alcohol-exposed pregnancy due to drinking while sexually active without effective contraception 1
• No amount of alcohol is safe during pregnancy—complete abstinence is the only way to prevent FAS 4, 5
• There is no safe trimester and no safe type of alcohol (beer, wine, liquor all pose equal risk) 5

Importance of Early Recognition

Early diagnosis leads to better outcomes through: 1

• Access to appropriate medical, educational, and social services 1
• Interventions that can improve adaptive functioning and reduce secondary disabilities 1
• Family support and education 1

The condition was first identified in 1973, yet many affected individuals remain undiagnosed due to lack of uniform diagnostic criteria and clinical awareness. 1