The answer is: Fetal alcohol spectrum disorder (FASD)
Fetal alcohol spectrum disorders (FASDs) are conditions that occur in a baby, as a result of alcohol assumption during pregnancy. Those conditions vary from short height (as in Barney's case) to low body weight, poor coordination, limited intelligence, problematic behavior, etc. Children with FASD usually face problems at school, and later display reckless behaviors. This often results in alcoholism or drug addiction.
