Potential effects of radiation have been extensively researched, resulting in a broad body of knowledge. As with any body of knowledge, uncertainties exist. The purpose of reviewing radiation research and the underlying uncertainties is to build a knowledge base from which reasonably informed clinical decisions can be reached about the risks of radiological examinations in pregnant or potentially pregnant women. Two issues of risk should be addressed: the likelihood of an adverse outcome, and the severity of the outcome. These should be weighed against the potential benefits to the pregnant patient and to the child.