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 findings show risk (but human findings do not) or, if no adequate human studies have been done, 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 justify the potential risk.

D

Positive evidence of risk

Investigational or postmarketing data show risk to fetus. Nevertheless, potential benefits may outweigh the risk.

X

Contraindicated in pregnancy

Studies in animals or humans, or investigational or postmarketing reports have shown fetal risk which clearly outweighs any possible benefit to the patient.