| Category A | Adequate, well-controlled studies in pregnant women have not shown an increased risk of fetal abnormalities. |
| Category B | Animal studies have revealed no evidence of harm to the fetus; however, there are no adequate and well-controlled studies in pregnant women. |
| or |
| Animal studies have shown an adverse effect, but adequate and well-controlled studies in pregnant women have failed to demonstrate a risk to the fetus. |
| Category C | Animal studies have shown an adverse effect and there are no adequate and well-controlled studies in pregnant women. |
| or |
| No animal studies have been conducted and there are no adequate and well-controlled studies in pregnant women. |
| Category D | Adequate well-controlled or observational studies in pregnant women have demonstrated a risk to the fetus. However, the benefits of therapy may outweigh the potential risk. |
| Category X | Adequate well-controlled or observational studies in animals or pregnant women have demonstrated positive evidence of fetal abnormalities. The use of the product is contraindicated in women who are or may become pregnant. |
| NA | A US Food and Drug Administration pregnancy rating is not available. |