SINCE the thalidomide tragedy of 1960 to 1962, pregnant women have been in a quandary about taking common medications on their own initiative, and physicians have been troubled about prescribing drugs for them. Peckham and King1have shown recently that 92% of women have at least one drug prescribed by their physicians during pregnancy, and 3.9% are given ten or more. There is no count of babies who have survived because of drugs administered during pregnancy, infants who escaped birth defects because their mothers were given certain drugs, or full-term babies who might have been born prematurely without drugs. Both physicians and patients rightly demand to know what information is available about drugs and human pregnancy. Very little is known that can actually be applied to all pregnancies. According to Lenz,280% of the mothers who took thalidomide during the period of fetal sensitivity had normal infants. What