A new study from Boston University's Slone Epidemiology Center, based on interviews with more than 20,000 new mothers, now provides important information for many of these medicines. The researchers considered antihistamines that had been suggested in earlier studies to increase risks of certain defects, and they also considered other possible risks that might not have been identified in the past. Where there was sufficient information in the study data, the authors found no evidence to support suggestions of risk that had been found in earlier studies. In considering possible risks that had not been identified by others, the investigators found very few suggestions that any given medicine might be linked to an increase risk of a specific birth defect, and though these few deserve further research attention, these findings may have been due to chance. The study currently appears in Journal of Allergy and Clinical Immunology: In Practice.

Dr. Allen Mitchell, the study's director, noted that "we were fortunate that our study was able to consider commonly-used antihistamines that were available OTC as well as those available only with a prescription. While our findings provide reassurance about the relative safety of many of these medications in relation to a number of common birth defects, more information is needed. As is the case for all types of medications, women who are pregnant or may become pregnant should consult with their health care provider before taking any medicines, whether they are prescribed or OTC."