The Food and Drug Administration offers the following classifications for prescription drugs that should not be taken during pregnancy:
Category C: These are drugs that are more likely to cause problems for the mother or fetus, and drugs for which safety studies have not been finished. The majority of these drugs do not have safety studies in progress. These drugs often come with a warning that they should be used only if the benefits of taking them outweigh the risks. This is something a woman would need to carefully discuss with her doctor. These drugs include prochlorperzaine (Compazine), Sudafed, fluconazole (Diflucan), and ciprofloxacin (Cipro). Some antidepressants are also included in this group.
Category D: These include drugs that have clear health risks for the fetus and include alcohol, lithium (used to treat manic depression), phenytoin (Dilantin), and most chemotherapy drugs to treat cancer. In some cases, chemotherapy drugs are given during pregnancy.
Category X: These drugs have been shown to cause birth defects and should never be taken during pregnancy. This includes drugs to treat skin conditions like cystic acne (Accutane) and psoriasis (Tegison or Soriatane); a sedative (thalidomide); and a drug to prevent miscarriage used up until 1971 in the U.S. and 1983 in Europe (diethylstilbestrol or DES).