FDA Pregnancy Category

Definition

Category A: Controlled studies show no risk: adequate, well-controlled studies in pregnant women have failed to demonstrate risk to the fetus. B: No evidence of risk in humans: either animal studies show risk, but human findings do not; or, if no adequate human studies have been performed, animal findings are negative. C: Risk cannot be ruled out: human studies are lacking and animal studies are either positive for fetal risk or lacking as well. However, potential benefits may outweigh risks. D: Positive evidence of risk: investigational or postmarketing data show risk to the fetus. Nevertheless, potential benefits may outweigh risks. X: Contraindicated in pregnancy: studies in animals or humans, or investigational or postmarketing reports, have shown fetal risks that clearly outweigh any possible benefit to the patient.