Table 2 Categories of risk for drugs during pregnancy [38]

A

These drugs are the safest. Well-designed studies in people show no risks to the fetus.

B

Studies in animals show no risk to the fetus, and no well-designed studies in people have been done.

or

Studies in animals show a risk to the fetus, but well-designed studies in people do not.

C

No adequate studies in animals or people have been done.

D

Evidence shows a risk to the human fetus, but benefits of the drug may outweigh risks in certain situations. For example, the mother may have a life-threatening disorder or a serious disorder that cannot be treated with safer drugs.

X

Risk to the fetus has been proved to outweigh any possible benefit.