Analgesics during pregnancy.

The thalidomide tragedy of the late 1950s clearly proved the need for caution, and questionable drug use should always be avoided. The teratogenic potential of a drug is related to dosage and time of administration. During blastogenesis, fetal death may occur; during embryogenesis, deformity may develop; and during the last trimester, functional anomalies or "covert embryopathy" may be seen. Finally, the benefit to risk ratio of every drug must be carefully weighed, and only those with proved safety to the feto-maternal unit should be prescribed. Aspirin may be administered to the pregnant woman as an anti-inflammatory agent but in the lowest therapeutic dosage. In the later stages of pregnancy, however, aspirin should be avoided since it may prolong labor, lead to greater blood loss during delivery, and increase the incidence of stillbirths. The pyrazolones, although not associated with teratogenic side effects, may lead to sometimes fatal agranulocytosis and, accordingly, are not recommended in pregnancy. Acetaminophen is the analgesic and antipyretic of choice during all phases of pregnancy.