We don't know what we don't study: the case for research on medication effects in pregnancy.

This Commentary addresses issues related to exposures to teratogens and makes the case for increased research into the safety of medication usage during pregnancy for mothers and fetuses. Not only are medications commonly used during pregnancy, but evidence points to an increasing prevalence and number of drug exposures experienced by the embryo or fetus, particularly during the critical first trimester of pregnancy. Although the first trimester represents a particularly vulnerable period of organogenesis, exposures during other gestational time periods may also be associated with deleterious outcomes. In addition to the changing (and in many cases unknown) risks to a developing fetus, other challenges to studying medication exposures and their effects during pregnancy include the dramatic changes in physiology that occur in pregnant women and the ethical dilemmas posed by including this vulnerable population in randomized controlled trials of safety and efficacy. However, without adequate knowledge of the pharmacokinetics, pharmacodynamics, efficacy, and safety of medication use in pregnancy, women may be under-dosed to minimize exposure or not treated at all, resulting in inadequate treatment and potential harm to the mother and her baby. The Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) is undertaking studies on medications and teratogenic exposures during pregnancy, including alcohol, maternal diabetes, oral hypoglycemic agents, and antiviral medications, through several of its research networks. Although this is a start, there is a critical need for further research on medications used during pregnancy, especially their effects on both the mother and her developing child.