Teratogen: Any agent that can disturb the development of an embryo or fetus. Teratogens may cause a birth defect in the child. Or a teratogen may halt the pregnancy outright. The classes of teratogens include radiation, maternal infections, chemicals, and drugs.
Drugs known to be capable of acting as teratogens include, but are by no means limited to, ACE inhibitors like benazepril (brand name: Lotensin), captopril (Capoten), enalapril (Vasotec), fosinopril sodium (Monopril), lisinopril (Zestril, Prinivil), lisinopril and hydrochlorothiazide (Zestoretic, Prinzide), quinapril (Accupril), and ramipril (Altace); the acne medication isotretinoin (Accutane, Retin-A); alcohol, whether ingested chronically or in binges; androgens (male hormones); the antibiotics tetracycline (Achromycin), doxycycline (Vibramycin), and streptomycin; blood-thinners, such as warfarin (Coumadin); seizure medications, including phenytoin (Dilantin), valproic acid (Depakene, Depakote, Valprotate), trimethadione (Tridione), paramethadione (Paradione), and carbamazepine (Tegretol); the anti- depressant/anti-manic drug lithium (Eskalith, Lithotab); antimetabolite/anticancer drugs methotrexate (Rheumatrex) and aminopterin; the antirheumatic agent and chelator penicillamine (Ciprimene, Depen); antithyroid drugs, such as thiouracil/propylthiouracil and carbimazole/methimazole; cocaine; DES (diethylstilbestrol), a hormone; and thalidomide (Thalomid). Obviously, alcohol and illegal or unnecessary drugs should never be used by women who are pregnant, or who plan to get pregnant. However, sometimes a medication necessary for health is also a teratogen: thyroid medication, blood thinners, and lithium are just a few examples. In these cases, female patients should work carefully with their doctors to determine if an alternative treatment is possible before and during pregnancy. In some cases the danger of birth defects is limited to a certain part of the pregnancy, and medication can be started again after that period has passed. Other medications can be safely restarted with the baby's birth. Some medications also pass through breast milk, however, and if they cannot be avoided the mother may need to choose formula feeding instead.