Category A
Adequate controlled trials performed in pregnant women do not show an increased risk of birth defects or fetal abnormalities.Examples: folic acid, levothyroxine (Synthroid)
Category B
Animal studies have not revealed an increased risk of birth defects or fetal abnormalities, but there are not adequate studies in pregnant women OR animal studies have shown an effect but adequate controlled trials in pregnant women have not shown an increased risk of birth defects or fetal abnormalities.Examples: ondansetron (Zofran), metformin (Glucophage)
Category C
Animal studies have shown an adverse effect and there are no studies in pregnant women OR no animal studies have been done and there are no adequate controlled trials in pregnant women.Examples: albuterol (Ventolin), sertraline (Zoloft)
Category D
Adequate controlled trials or observational studies in pregnant women have proven an increased risk of birth defects or fetal abnormalities. However, benefits of therapy may outweigh the risks involved.Examples: paroxetine (Paxil), phenytoin (Dilantin)
Category X
Adequate controlled trials or observational studies in pregnant women and/or animals have proven an increased risk of birth defects or fetal abnormalities. These medications are contraindicated during pregnancy.Examples: isotretinoin (Accutane), warfarin (Coumadin)
Over-the-Counter (OTC) Medications
OTC medications do not have pregnancy letter categories unless they were previously a prescription mediation. Your healthcare provider can help you determine which OTC medications may be right for treating your headaches or other medical conditions.Sources:
Meadows, Michelle. Pregnancy and the drug dilemma. U.S. Food and Drug Administration, FDA Consumer magazine, May-June 2001.
The National Women’s Health Information Center. Frequently asked questions: pregnancy and medications. U.S. Department of Health and Human Services. Accessed: January 31, 2008. http://www.4woman.gov/faq/pregnancy-medicines.cfm
