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, excess vitamin A, excess retinoic acid, the rubella virus, and high levels of ionizing radiation. Perhaps the best-known teratogenic agent is the drug thalidomide, which in the 1950s and 1960s induced severe limb abnormalities, known as phocomelia, in children whose mothers were prescribed the drug to relieve morning sickness.

  This information is not a tool for self-diagnosis or a substitute for professional care.