Alcohol abuse during pregnancy can cause what's called Fetal-Alcohol Syndrome (FAS), associated with deformed teeth and facial features and mental retardation. (FAS is the leading preventable cause of mental retardation.)
Because no conclusive studies have been done on just how many drinks you can have while pregnant before harming your baby, experts suggest you steer clear of drinking.
Methamphetamine (Meth) and Ecstasy are popular chemical cousins of the drug amphetamine, a substance which causes the heart rate to increase (to dangerously high levels). Women who take methamphetamine during pregnancy see similar problems as women taking cocaine during pregnancy.
The use of amphetamines speeds up the user's system and can cause the baby to get less oxygen, leading to a low birth weight baby.
According to the American Pregnancy Association (APA), Meth and Ecstasy can also increase the likelihood of premature labor, miscarriage, and placental abruption. Babies whose mothers take amphetamines during pregnancy are often born addicted to the drug and suffer withdrawal symptoms (such as tremors, sleeplessness, muscle spasms, and difficulties feeding).