| 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 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. |
