Fetal alcohol syndrome (FAS) is the leading known preventable cause of non-inherited mental retardation and birth defects, and is the most extreme case of prenatal alcohol exposure. It is diagnosed by the presence of facial abnormalities (small palprebral fissures, flattened filtrum and thin upper lip), growth deficiency (reduced head circumference, height and weight deficiency), central nervous system dysfunction (cognitive and neurobehavioral problems), and a confirmed history of prenatal alcohol exposure.

Blood vessels in the placenta provide nourishment and oxygen from a mother's body to her developing infant. When she drinks alcohol , it enters both the blood streams of her own body and that of her unborn child's body. A spectrum of neurobehavioral, cognitive and physical abnormalities can therefore exist, even in the absence of the criteria necessary for a diagnosis of FAS. These disabilities can be as devastating to the functioning of these individuals and their families as FAS, even without the mental retardation, growth deficits or dysmorphic facial features.

All women of child bearing age should understand that there is, at this time, no known minimum amount of alcohol that can be consumed safely during pregnancy. Alcohol therefore should never be consumed if the women expects to become pregnant or is already pregnant. Prenatal alcohol related disability is one of the most preventable causes of cognitive and neurobehavioral disability.