Teratogenesis

Teratogenesis: A medical term from the Greek, literally meaning monster making. It has gained a more specific usage for the development of abnormal cell masses during fetal growth, causing physical defects in the fetus.

There are a large number of teratogenic materials, Thalidomide is a well known example. The Rubella (German measles) virus is also teratogenic, as is use of large amounts of alcohol during pregnancy.