Chronic use of the antifungal drug, fluconazole, during pregnancy may cause birth defects, according to the U.S. Food and Drug Administration. Specifically, the regulatory agency is informing the public that long-term, high-dose use of products like Pfizer’s Diflucan during the first trimester of pregnancy may lead to a rare set of birth defects in infants.

The FDA has ordered new labeling for fluconazole in order to better warn consumers of the risks associated with use of the drug. In fact, given this new information, when used in doses ranging from 400-800mg a day, Diflucan’s classification has been changed from category C to a category D drug. The link between Diflucan and birth defects does not appear to be associated with single, low doses of the drug.

The FDA recommends that healthcare professionals counsel patients regarding the potential risks if the drug is used during pregnancy or if a patient becomes pregnant while on taking the drug. The agency also encourages doctors and patients to report any adverse events experienced as a result of using fluconazole.