Table 2.

FDA pregnancy categories [www.fda.gov].

Category	Interpretation
A	Controlled studies show no risk. Adequate, well-controlled studies in pregnant woman have failed to demonstrate a risk to the foetus in any trimester of pregnancy.
B	No evidence of risk in humans. Adequate, well-controlled studies in pregnant woman have not shown in creased risk of metal abnormalities despite adverse findings in animals, or, in the absence of adequate human studies, animal studies show no fetal risk. The chance of metal harm is remote, but remains a possibility.
C	Risk cannot be ruled out. Adequate, well-controlled human studies are lacking, and animal studies have shown a risk to the foetus or are lacking as well. There is a chance of metal harm if the drug is administered during pregnancy, but the potential benefits may outweigh the potential risk.
D	Positive evidence of risk. Studies in humans, or investigational or postmarking data, have demonstrated metal risk. Nevertheless, potential benefits from the use of the drug may outweigh the potential risk.
X	Contraindicated in pregnancy. Studies in animal or human, or investigational or postmarketing reports, have demonstrated positive evidence of metal abnormalities or risk that clearly outweighs any possible benefit to the patient.