Embryology · Teratology and prenatal diagnosis
Alcohol: fetal alcohol spectrum disorder !
- Teratogen
Alcohol in pregnancy can affect the baby's brain, face and growth; no amount or time is known to be safe.
Updated 2026-11-01
See it in 3D: Corpus callosum · Maxillae · Frontal lobe
What it is
Alcohol crosses the placenta and is teratogenic in all three trimesters. Its effects range from mild learning and behaviour problems to fetal alcohol syndrome, with typical facial features, growth deficiency and central nervous system damage. It is a preventable cause of intellectual disability, and no amount or time in pregnancy is known to be safe for drinking.
Key facts
- First trimester: linked to the facial and brain anomalies.
- Third trimester: linked to smaller length, weight and brain volume.
- Other defects: heart, kidney, bones, eyes and hearing.
- Also linked to miscarriage, preterm birth, placental abruption and stillbirth.
- Severe cases may show holoprosencephaly or agenesis of the corpus callosum.
Critical period and mechanism
- Critical period: the whole pregnancy; the face is shaped in weeks 3 to 8, and the brain keeps growing to term.
- It reduces proliferation and increases death of cranial neural crest cells, which build the bones and tissues of the face.
- It injures neurons and disturbs their migration, reducing brain volume.
- Brain damage is irreversible; its degree depends on how much, when and how often alcohol is drunk.
Prevention
- Avoiding all alcohol during pregnancy and while trying to conceive.
- A pregnancy can go unnoticed for 4 to 6 weeks, so abstaining starts earlier.
- Stopping at any point helps the baby, because the brain keeps growing.
What it does to the embryo and fetus
- Face: smooth philtrum, thin upper lip, short palpebral fissures, maxillary hypoplasia, depressed nasal bridge.
- Growth: low weight and length, microcephaly.
- Infant: irritability and developmental delay; child: hyperactivity and school difficulties, sometimes mistaken for ADHD.
- Heart, kidney, skeletal, eye and hearing defects.
Test yourself
Think of the answer, then tap the question to see it.
What are the three characteristic facial features of fetal alcohol syndrome?
Smooth philtrum, thin upper lip vermilion and short palpebral fissures.
Which embryonic cells explain the facial features of fetal alcohol syndrome?
Cranial neural crest cells: alcohol reduces their proliferation and increases their death.
Is there an amount or a trimester in which alcohol is safe in pregnancy?
No. No safe amount or time is known; alcohol is teratogenic in all three trimesters.
See it in 3D
The structures of Durgical's 3D anatomy where it is found.
Related
- Neural crest cells and their derivatives
- The face: five prominences
- Microcephaly
- Holoprosencephaly
- Principles of teratology: critical periods, dose and genotype
- Fetal growth and growth restriction
Related conditions
- Alcohol use disorder
- Attention-deficit/hyperactivity disorder (ADHD)
- Miscarriage (early pregnancy loss)
- Placental abruption
Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given.
Sources: About Fetal Alcohol Spectrum Disorders (FASDs) (CDC, 2024); Fetal Alcohol Syndrome (StatPearls Publishing (NCBI Bookshelf), 2026); Substance Use During Pregnancy (CDC, 2024).
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Representative model, for educational purposes only.