Environmental agent that interrupts the normal development of an organism, especially a fetus.

A teratogen, also referred to as a teratogenic agent, is an environmental agent that can cause abnormalities in a developing organism, resulting in either fetal death or congenital abnormality. The human fetus is separated from the mother by the placental barrier, but the barrier is imperfect and permits a number of chemical and infectious agents to pass to the fetus. Well-known teratogens include (but are not limited to) alcohol, vitamin A and retinoic acid in excessive doses, the rubella virus, the syphilis bacterium, and high levels of ionizing radiation. In the 1960s, it was discovered that the tranquilizer thalidomide had serious side effects when taken during pregnancy. Although thalidomide was never sold legally in the United States, it was available elsewhere in the world and prescribed freely during the 1940s and 1960s. It was later shown to induce birth defects, especially severe limb abnormalities known as phocomelia, in children whose mothers took the drug.

In the 1970s, a study of birth defects among babies born to women who had taken lithium during at least the first trimester of pregnancy seemed to link lithium to birth defects, especially in congenital cardiovascular abnormalities. However, subsequent studies in the 1990s have questioned the adverse effects of lithium on fetal development. Today, many physicians treating pregnant women who take lithium as medication for a bipolar disorder carefully weigh the risk posed by lithium against the effects of discontinuing medication.

For Further Study

Books

Fine, Ralph. The Great Drug Deception. New York: Stein and Day, 1972.

Kelley-Buchanan, Christine. Peace of Mind During Pregnancy: An A-Z Guide to the Substances that Could Affect Your Unborn Baby. New York: Dell Publishing, 1989.

Roskies, Ethel. Abnormality and Normality: The Mothering of Thalidomide Children. Ithaca, New York: Cornell University, 1972.