ABSTRACT
The epidemiologic, post approval study of the reproductive effects of any drug poses numerous methodologic and practical challenges. Detection of any but an extremely large increase in the risk of specific birth defects would require the observation of immensely large numbers of pregnancies because of the low frequency of birth defects and the low rates of exposure. A voluntary registry of exposures to isotretinoin, a known human teratogen, demonstrated a significant difference in rates of abnormalities among pregnancies reported prospectively, and those reported retrospectively. Spontaneous abortions, which occur more frequently than birth defects, could be assessed in a population where pregnancies are detected early and reflected in the data bases. The principal effort to address the safety-in-pregnancy question was through the Acyclovir in Pregnancy Registry, a case-registration study established by Burroughs Wellcome Co. in January 1985. The case-registration approach is substantially strengthened through the collaborative efforts of the Acyclovir in Pregnancy Registry Advisory Committee in three ways.
