Alcohol Exposure During Pregnancy: Understanding Risks & Effects

Alcohol Transfer to Fetus: Mechanism and Consequences

Alcohol crosses the placenta freely. The fetus lacks metabolic capacity, leading to prolonged exposure and teratogenic effects.

Transfer Pathway

1. Maternal ingestion → GI absorption → portal vein → systemic circulation.
2. Maternal blood → placental intervillous space.
3. Passive diffusion across placental membranes (ethanol is small, lipid/water soluble).
4. Fetal circulation → fetal tissues.
5. Fetal liver: minimal ADH/ALDH activity → prolonged half-life (amniotic fluid acts as reservoir).
6. Fetal swallowing/urinating → recirculation in amniotic fluid.

Fetal Alcohol Spectrum Disorders (FASD)

• Fetal Alcohol Syndrome (FAS): Growth deficiency, characteristic facies (smooth philtrum, thin vermillion, small palpebral fissures), CNS abnormalities.
• Partial FAS, ARND, ARBD: Neurobehavioral deficits without full dysmorphology.
• Effects: ID, ADHD, executive dysfunction, learning disabilities, behavioral problems, birth defects (heart, kidney, skeletal, vision, hearing).

Critical Principles

• No safe amount, no safe time, no safe type.
• Damage can occur before pregnancy recognition.
• Binge drinking especially harmful (peak BAC).
• Paternal alcohol may affect sperm epigenetics (emerging evidence).

Prevention

• Abstain when trying to conceive and throughout pregnancy.
• Screening (AUDIT-C) at prenatal visits.
• Support for cessation (counseling, medication if AUD).

FASD is 100% preventable.