Fetal alcohol syndrome, or FAS, occurs because of maternal use of alcohol during pregnancy.
It’s currently the leading cause of intellectual disability in the US and can cause characteristic physical abnormalities.
Normally, the fetus is connected to the placenta by the umbilical cord, so the fetus gets oxygen and nutrients from the mother.
Unfortunately, ethanol and toxic alcohol metabolites like acetaldehyde also pass freely through the placenta, but the fetal liver doesn’t have the necessary enzymes to metabolize them, so they build up inside the fetus really fast.
In FAS, ethanol interferes with cell division and proliferation, cell growth and differentiation, and with the migration of mature cells to their final location in the developing embryo, which affects the development of various fetal tissues, including the brain.
Alcohol-induced brain damage includes partial or complete agenesis of the corpus callosum, which links the two hemispheres together, so it either forms incompletely, or not at all.
This causes intellectual disability and seizures.
When the frontal cortex and the hippocampus are affected, this causes poor memory and communication skills, as well as intellectual disability.
The cerebellum can also be smaller in size, called hypoplasia, leading to trouble with movement and balance.
The most common symptom of FAS is growth retardation, resulting in low height and weight.