OBJECTIVE: The lack of human data available to inform evidence-based treatment for illness during pregnancy has led to calls for greater inclusion of pregnant women in research, but the extent of their current representation is poorly characterized. Our objective was to measure the current exclusion of pregnant women from industry-sponsored clinical trials as a baseline for future comparison. METHODS: We compiled data from studies enrolling women of childbearing potential posted on www.ClinicalTrials.gov between 1 October 2011 and 31 January 2012. The review was limited to open United States-based phase IV interventional studies sponsored by the pharmaceutical industry evaluating treatment of conditions that may be experienced by but are not limited to pregnant women and did not involve a medication classified as potentially teratogenic. If there was no mention of pregnancy in the inclusion or exclusion criteria, we contacted a study representative to confirm that pregnant women could be enrolled. RESULTS: Of 558 qualifying industry-sponsored studies, five (1%) were designed specifically for pregnant women. Of 367 phase IV clinical trials with verified inclusion and exclusion criteria, 348 (95%) excluded pregnant women and 19 (5%) did not. CONCLUSION: We found the exclusion of pregnant women from industry-sponsored clinical trials to be common practice. Moving beyond reflexive exclusion and developing thoughtful criteria for inclusion of pregnant women in clinical research would likely advance the evidence base to inform treatment decisions during pregnancy and lead to better health outcomes for women and children.