Abstract
Patients, prescribers, and policymakers often assume that the most serious short-term adverse effects of a drug are identified in pre-marketing studies, so recognition of unexpected harm after widespread use raises concern about “failures of the system.” For drug-induced birth defects, however, the situation is reversed: the unfortunate reality is that we learn about virtually all teratogenic effects only after a drug has already received marketing approval, and of course, only after it has been used by pregnant women. Indeed, some teratogenic effects may be identified only after the drug has been in use for many decades. In these situations, the . . .