Each of these medications, if taken early in pregnancy, can cause abnormalities that may be subtle and difficult to identify through our usual prenatal ultrasound studies. For these reasons, we strongly suggest that women taking medications prior to initiating pregnancy consult with their obstetricians or a geneticist. Alcohol and tobacco also expose a pregnancy to additional risks. No safe level of alcohol intake in pregnancy has ever been established. For that reason, the safest course is to avoid alcohol altogether.
Cigarettes cause problems as well because they decrease the supply of oxygen across the placenta.
They restrict the fetus' growth and affect the function of the placenta. Women who are smokers should seriously consider stopping smoking before they begin pregnancy. Cocaine has also been associated with structural abnormalities in pregnancies and should be avoided. I can unambiguously say that the safest pregnancy is one where there is minimal drug exposure. Although there are clearly safe medications for use during pregnancy, many can have adverse effects.