Given the unique nature of pregnancy with respect to obtaining safety data regarding medication exposures, developing comprehensive information on the wide variety of medications that might be of clinical benefit during pregnancy is a challenging and on-going task. For many of the most commonly used asthma and allergy medications that were covered in this article, there is at least limited human data are available. Even for relatively well-studied medications, there are many unanswered questions, and few studies exist that are large enough to rule out at least a doubling of risk for specific outcomes, particularly congenital anomalies. This challenge becomes even more daunting when evaluating risks of individual products is considered the optimal goal, as opposed to "lumping" all medication exposures within a class. All of these issues call for more human pregnancy data that are collected more efficiently so that the answers that clinicians and pregnant women need are available more readily. In the meantime, health care providers and pregnant women must work with the information that is available to evaluate the risks and benefits of a particular medication and alternative choices for treatment of asthma or allergy during pregnancy, while considering the potential for adverse effects if the woman with severe or uncontrolled asthma is under-treated. To assist in making a risk/benefit assessment, the clinician can draw on existing resources that provide systematic periodic review of new data on medications in pregnancy as it becomes available, and synthesize the entire body of data on a particular drug into concise summary statements. Two such resources are TERIS (TeratogenInformation System)  and Reprotox ; both on-line services are managed by experts in the field of teratology. An additional resource for clinicians and pregnant women is the Organization of Teratology Information Specialists , a network of risk-assessment counselors in the United States and Canada who specialize in research and the communication of risks that are associated with exposures in pregnancy.