Should pregnant women be included in phase IV clinical drug trials?

Relatively few drugs, especially those recently approved by the US Food and Drug Administration, have published human pregnancy experience. Although all drugs contain animal reproduction data, these are usually not predictive of human risk. Clinical trials in pregnant women are rarely conducted because of ethical and legal concerns, and it may be many years before sufficient observational data are collected to guide clinical treatment decisions. Because many of these drugs will be used in pregnancy, human data are needed shortly after the drugs come to the market. Lack of human data leads to uncertainty over whether a drug can be safely prescribed for a pregnant patient. Unless there are compelling scientific and ethical reasons to exclude them, pregnant women should be included in phase IV clinical trials (postmarketing studies to obtain additional information, including the risks, benefits, and optimal use of a drug). This paper examines how physicians currently counsel pregnant women when there are no human data and proposes an alternative method in which knowledge regarding risks associated with the use of drugs during pregnancy can be enhanced in a clinical trial setting.