Table 8.2-1. US Food and Drug Administration pregnancy risk categories

Category

Interpretation

A

Controlled human studies show no risk

B

No evidence of risk in studies. Either animal studies have not demonstrated a fetal risk and no controlled human studies exist or animal studies have shown an adverse effect that was not confirmed in controlled human studies

C

Risk cannot be excluded. Either animal studies have revealed adverse effects on the fetus and there are no controlled human studies or studies in women and animals are not available. Only administer the drug if the potential benefits outweigh the potential risk to the fetus

D

Evidence of human fetal risk. Only administer the drug if the potential benefits outweigh the known risk to the fetus

X

Contraindicated in pregnancy