In 1975, the FDA introduced categories
to determine if a medication would be safe for pregnancy. Over the years, it
has become clear that drug safety in pregnancy isn’t always quite that easy. A
new system of defining drug safety in pregnancy is due out in the future but
has yet to be introduced. In the meanwhile, we are left with the system
introduced in 1975, and still currently in place, to decide medication safety
for pregnancy. It is important that women who are pregnant, or considering
pregnancy, understand the drug categories and what they mean.
are the categories?
The categories are lettered A, B, C,
D, and X. Their definitions are as
A – Controlled studies in pregnant women
demonstrated no risk to the fetus during any part of the pregnancy, examples
are folic acid and vitamin B6.
B – No adequate controlled studies in pregnant
women exist and animal studies show no fetal risk, examples are Tylenol and
C – No adequate controlled studies in pregnant
women exist and animal studies show adverse fetal risk that may be outweighed by the benefit of the drug, examples are Ciprofloxacin and
D – Studies in humans, investigational or post
marketing data, have demonstrated fetal risk that may be outweighed by the
benefit of the drug, examples are Dilantin and most chemotherapy drugs.
X – Studies in humans or animals,
investigational or post marketing data, demonstrate fetal abnormalities or risk
that outweighs any possible drug benefit, examples are accutane and
how does this translate into practice?
Anyone looking at this would think,
“well, just take category A drugs of course.” The truth is category A drugs are
very few. Controlled studies in pregnant women just don’t happen because of the
fetal risk if something goes wrong. The majority of “safe drugs” are actually
category B drugs and as a provider category B always gets the green light.
Category C and D drugs are a little
trickier. They are used--but only in situations where the benefit of the drug
will outweigh the risk to the fetus. That is an important decision that is made
by your provider prescribing the medication. Finally, pregnant women or those
planning pregnancy should never take category X drugs. So if you are pregnant or planning to be
pregnant, review your medications with your provider and make sure they are
safe for you and your baby.