Slone Center Study Evaluates Antihistamine Use in Pregnancy.

A team led by BUSPH researchers has found no “meaningful support” for previous suggestions that antihistamines taken during pregnancy might be linked to increased risks of birth defects.

In a study in the Journal of Allergy and Clinical Immunology: In Practice, researchers with the Slone Epidemiology Center tested16 previously hypothesized associations between specific antihistamines and specific birth defects. The team used 1998-2010 data from the Slone Epidemiology Center Birth Defects Study, a multi-center case-control surveillance program of birth defects in North America.

Dr. Allen MitchellAntihistamines are a group of medications that are used to treat various conditions, including allergies and nausea and vomiting. Some antihistamines require a prescription, but most are available over-the-counter. Until recently, little information was available to women and their health-care providers on the possible risks and relative safety of these medications in pregnancy, particularly when it came to specific birth defects.

The new study was based on interviews with more than 20,000 new mothers. The researchers considered antihistamines that had been suggested in earlier studies to increase risks of certain defects, while also considering other possible risks that might not have been identified in the past.

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 previously, the investigators found very few suggestions that any given medicine might be linked to an increased risk of a specific birth defect. And although those few deserve further research attention, the findings may have been due to chance, the researchers said.

“We suspect that previous associations may be chance findings in the context of multiple comparisons, a situation that may also apply to our new findings,” the authors said.

Dr. Allen Mitchell, the study’s director, who is a professor of epidemiology at BUSPH and of pediatrics at the School of Medicine, said that while the 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 over-the-counter, he said.

Besides Mitchell, Martha M. Werler, BUSPH professor of epidemiology, and researchers from the Harvard School of Public Health participated in the study.