Fetal Alcohol Syndrome (FAS): Causes, Symptoms & Prevention

How Alcohol Damages the Developing Fetus

When a pregnant woman drinks, alcohol crosses the placenta freely and reaches the fetus at concentrations equal to the mother's blood alcohol level. However, the fetus metabolizes alcohol far more slowly than an adult because its liver is immature. This means the fetus is exposed to alcohol for longer periods. Alcohol disrupts fetal development by killing developing neurons, interfering with cell migration and differentiation, disrupting the formation of neural connections, damaging DNA, and reducing blood flow to the placenta. The brain is particularly vulnerable throughout pregnancy, but different structures are at risk during different trimesters.

Types of Fetal Alcohol Spectrum Disorders

• •Fetal Alcohol Syndrome (FAS) — the most severe form with distinctive facial features, growth deficiency, and CNS damage
• •Partial Fetal Alcohol Syndrome (pFAS) — some but not all facial features, with confirmed prenatal alcohol exposure
• •Alcohol-Related Neurodevelopmental Disorder (ARND) — behavioral and cognitive problems without distinctive facial features
• •Alcohol-Related Birth Defects (ARBD) — physical abnormalities of the heart, kidneys, bones, or other organs
• •Neurobehavioral Disorder Associated with Prenatal Alcohol Exposure (ND-PAE) — newly defined in DSM-5, focuses on neurocognitive impairment

Recognizing Fetal Alcohol Syndrome

FAS is diagnosed based on a triad of features: characteristic facial abnormalities (smooth philtrum, thin upper lip, short palpebral fissures), growth deficiency (height and/or weight below 10th percentile), and central nervous system damage (structural brain abnormalities, cognitive impairment, or behavioral problems). Not all children with prenatal alcohol exposure will show all three features — which is why the broader term FASD encompasses the full range of effects.

Lifelong Effects of Fetal Alcohol Exposure

• •Intellectual disability — IQ ranges from 20-120 but averages around 70
• •Learning disabilities — difficulty with math, memory, attention, and abstract thinking
• •Behavioral problems — impulsivity, poor judgment, difficulty understanding consequences
• •Social skill deficits — difficulty reading social cues, maintaining friendships, and understanding boundaries
• •Mental health disorders — ADHD, anxiety, depression, and conduct disorder are common comorbidities
• •Independent living challenges — adults with FASD often struggle with employment, finances, and daily tasks
• •Legal problems — poor judgment and impulsivity contribute to higher rates of involvement with the justice system
• •Secondary disabilities — substance abuse, mental health problems, and disrupted school experience affect 90%+ of individuals with FAS

Prevention: The Only Solution

FASD is 100% preventable. The single most effective intervention is abstaining from alcohol during pregnancy. Women who are trying to conceive should also abstain, as many pregnancies are unplanned and alcohol exposure during the earliest weeks — before a woman knows she is pregnant — can cause significant damage. If you are pregnant and struggling to stop drinking, this is a medical situation that requires professional help, not judgment. Treatment programs exist specifically for pregnant women with substance use disorders.

Getting Help If You Are Pregnant and Drinking

If you are pregnant and unable to stop drinking, contact your healthcare provider immediately. You can also call the SAMHSA National Helpline at 1-800-662-4357 for free, confidential referrals to treatment programs that serve pregnant women. Many programs offer comprehensive services including prenatal care, addiction treatment, mental health support, and case management. Stopping alcohol use at any point during pregnancy reduces the risk of further harm to the fetus — it is never too late to stop.

Related Resources