Assessment of teratogenicity

Animal tests for teratogenicity of drugs have more medicolegal and political significance than relevance to human therapeutics. Test conditions differ widely from human therapeutic regimens and major species differences are common. Occasionally the tests will define a drug or group of drugs with an unpleasant potential, and sometimes a mode of action which needs careful exploration in humans will be found. Anecdotal case reports of purported associations between drug use and congenital malformations provide a vast source of misinformation, yet they were responsible for the indictment of thalidomide as a human teratogen. Retrospective studies on patients who have taken a drug in pregnancy are susceptible to recall bias, and at best provide a basis for planned prospective studies which are seldom instituted for fear of medicolegal consequences. Prospective surveillance of drugs already accepted for use in pregnancy and reporting of `adverse reactions' to drugs inadvertently used in pregnancy thus provide the only effective source of information on teratogenicity of psychotropic drugs in humans.