Table 1-2. FDA pregnancy categories. The following definitions have been
established to assign drugs to appropriate categories for use in pregnant
women. Modified and reproduced from FDA Drug Bulletin, 1982; 12: 24.
Regardless of the designated Pregnancy Category or presumed safety, no drug
should be administered during pregnancy unless it is clearly needed.
A Controlled studies in women fail to demonstrate a risk to the
fetus in the first trimester, and the possibility of fetal
(Safest) harm seems remote.
B Animal studies do not indicate a risk to the fetus and there
are no controlled human studies,
animal studies do show an adverse effect on the fetus but
well-controlled studies in pregnant women have failed to
demonstrate a risk to the fetus.
C Studies have shown the drug to have animal teratogenic or
embryocidal effects, but there are no controlled studies in
no studies are available in either animals or women.
D Positive evidence of human fetal risk exists, but benefits
in certain situations (eg, life-threatening situations or
diseases for which safer drugs cannot be used or are
ineffective) may make use of the drug acceptable despite its
X Studies in animals or humans have demonstrated fetal abnormal-
ities or there is evidence of fetal risk based on human
(Least experience, or both, and the risk clearly outweighs any
safe) possible benefit.
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