 FAS disrupts normal development of the fetus, which may cause certain developmental stages to be delayed, skipped, or immaturely developed.Since alcohol elimination is slow in a fetus than in an adult and the fact that they do not have a developed liver to metabolize the alcohol, alcohol levels tend to remain high and stay in the fetus longer.Birth defects associated with prenatal exposure to alcohol can occur in the first three to eight weeks of pregnancy before a woman even knows that she is pregnant.