Category A |
Adequate studies in pregnant women have failed to show a risk to the fetus in the first trimester and there is no evidence of risk in later trimesters. |
Category B |
Animal studies have failed to show a risk to the fetus but there are no adequate studies in pregnant women: or animal studies have shown an adverse effect but human studies have not shown a risk to the fetus in the first trimester and there is no evidence of risk in later trimesters. |
Category C |
Animal studies have shown an adverse effect on the fetus but there are no adequate studies in humans, but the benefits may outweigh the risks; or there are no aminal studies and no adequate human studies. |
Category D |
Positive evidence of human fetal risk but the benefits may outweigh the risks. |
Category X |
Animal or human studies have shown fetal abnormalities or toxicity, and the risk outweighs the benefits. |