Despite scientific advances in clinical teratology, exposures during pregnancy still cause great anxiety and misunderstanding. Patients and health care providers are frequently called upon to determine the health implications of scientific studies, which may involve limited and contradictory data. These findings are often conveyed numerically, which is a particularly difficult form of information for both patients and their health providers to understand and interpret. Almost half of the general population (and a substantial minority of physicians) have difficulty with numeracy. Patients with low numeracy tend to interpret information in an absolute manner and ignore uncertainty, have more difficulty using numeric information to inform their choices, and are more easily influenced by emotion and the format used in presenting information. Formats involved in conveying probability include positive or negative framing, use of relative versus absolute risk, and ratios and percentages. Health providers should communicate risk analysis in a fashion that facilitates comprehension and results in informed behavior. This is more likely to be achieved when risks are conceptualized as more than just numbers, and are considered in the context of individuals' life circumstances and values. Most teratogen risk communication is done over the telephone; this presents both advantages and challenges. Strategies are suggested to improve risk communication. These include avoiding the use of relative risk, using a consistent denominator, framing the information in a variety of ways (positive vs. negative), using verbal qualifiers judiciously, and employing visual aids. © 2011 Wiley-Liss, Inc.