Overview
What is FASD?
Fetal Alcohol Spectrum Disorders (FASD) is an umbrella term describing a range of conditions that can occur in a person whose mother consumed alcohol during pregnancy. The effects can include physical, mental, behavioural, and learning disabilities with lifelong implications.
Alcohol is a teratogen — a substance toxic to the baby's developing brain. Because the brain and central nervous system develop throughout the entire pregnancy, the baby is always vulnerable to damage from alcohol at any stage.
Pre-natal alcohol exposure can cause damage in various regions of the brain. The areas affected depend on which areas are developing at the time the alcohol is consumed.
Key Features
Growth Deficiency
Significantly below-average height and weight, often present from birth and persisting throughout childhood.
Small Head Circumference
Microcephaly reflects reduced brain growth resulting from prenatal alcohol exposure.
Characteristic Facial Features
Specific features including a smooth philtrum, thin upper lip, and small eye openings.
Behavioural Difficulties
Challenges with attention, impulse control, social skills, and adaptive behaviour from neurological differences.
Neuroscience
Prenatal Alcohol Exposure & the Brain
Alcohol passes freely through the placenta and reaches the developing fetus at concentrations similar to those in the mother's bloodstream. Unlike the adult brain, the fetal brain has no protective mechanism against this exposure.
The damage depends heavily on timing, quantity, and frequency of exposure. Because different brain regions develop at different stages, even moderate drinking at a critical period can cause irreversible structural or functional changes.
Vulnerability of the fetus leads to defects during different periods of development. The most sensitive periods result in major structural abnormalities, while less sensitive periods may cause physiological defects and minor structural abnormalities.
By Trimester
First Trimester
Brain Cell Migration
Research shows alcohol interferes with the migration and organisation of brain cells during the first trimester — laying the foundation for later cognitive and structural problems.
Journal of Pediatrics, 92(1):64–67
Second Trimester
Clinical FAS Features
Heavy drinking during the second trimester — particularly weeks 10–20 after conception — appears to produce the most pronounced clinical features of FAS.
Early Human Development, 1983 Jul, Vol. 8(2):99–111
Third Trimester
Hippocampal Impact
The hippocampus is greatly affected during the third trimester, leading to problems with encoding visual and auditory information — affecting reading and mathematical ability.
Neurotoxicology and Teratology, 13:357–367, 1991
Developmental Sensitivity
Stages of Fetal Vulnerability
Each organ has its own critical window. The chart below shows the relative sensitivity of major structures across the three trimesters — showing when teratogenic damage risk is highest.
Development Timeline
Three phases of fetal development — tap any phase to expand.
Conception
Formation
Formation of a viable zygote by the union of male sperm and female ovum. Normal hormonal balance and a healthy cycle are essential foundations.
Embryonic Development — Weeks 1.5 to 12
1.5 Weeks
Completely developed embryo at this earliest stage.
3rd Week
Central nervous system begins developing. Heart development initiated — beating begins.
4th Week
About 2.5 cm. Out-pouchings from the anterior brain form early eyes; limb buds appear.
5th Week
Nose and lip formation begins. Brain develops into 5 components; cerebrospinal fluid flow begins.
8th Week
Major organs begin development. ~2.5 cm, ~4g. Hands and feet visible. Baby is extremely reactive to its environment.
12th Week
Placenta well established, weighs more than baby (~8.8 cm, ~60g). Fingers and toes visible. End of embryonic stage.
Fetal Development — Weeks 14 to 40
14–16 Weeks
Brain developed enough that baby can suck, swallow, and make irregular breathing movements.
16 Weeks
15.2 cm, 180g. Nasal septum and palate close. Fetal heartbeat heard. Sex distinguishable.
20 Weeks
20.3 cm, 300g. Fetal heartbeat: 120–160 bpm.
24 Weeks
30.4 cm, 720g. Maturing but not yet viable outside the uterus.
28 Weeks
35.6 cm, 1 100g. 10–20% survival if born now. Legally viable.
32 Weeks
35.5 cm, 1 680g. 50% survival. Skin is red and wrinkled.
36 Weeks
45.7 cm, 2 500g. 94% survival. Fingernails reach fingertips.
40 Weeks — Full Term
50.8 cm, 3 360g. All major systems mature and ready for life outside the womb.
Need support or information?
Visit our support section for resources on living with FASD, or get in touch with our team directly.