Demystifying Drug Categories for Pregnant Women

Category B
Drugs assigned a category B rating are not likely to pose a threat to the fetus from the evidence in animal studies, but no well-controlled studies have been performed in pregnant women. However, a drug may also receive a category B rating if animal studies have shown evidence of fetus damage but the same drug tested on pregnant women posed no threat.

Category C
A category C rating is given to drugs that have been shown to be harmful in animal studies but no studies have been conducted on pregnant humans. Drugs may also receive a category C rating if the drug was not studied in animals and there isn't enough evidence from studies in pregnant humans. This implies that the drug may or may not be safe to take.

Category D
Drugs receive a category D rating when the drugs have been tested in well-controlled or observational (not controlled) studies, which resulted in harm to the unborn baby. In some cases these drugs may still be given if the benefits to the mother outweigh the risks to the baby (for example, cancer treatment).

Category X
A Category X rating is assigned to drugs that should never be used during pregnancy, as there are no benefits that would exceed the potential risk.

Continued Surveillance

The FDA is continually monitoring the safety of drugs during pregnancy. The drug manufacturers are required to collect feedback from pregnant women who are taking their drug, and to report these findings to the FDA.

Ultimately, all drug treatment decisions during pregnancy should be made under the guidance of a physician. To ensure the best outcome for you and your baby, discuss all over-the-counter drugs, prescription medications, dietary supplements and herbal preparations with your doctor.

Copyright © Jodi Razgaitis. Permission to republish granted to, LLC.


The FDA is in the process of revising this system and getting rid of the alphabet soup in favor of more detailed info. There are several problems with this system. For example, the system makes it sound like a B is better than a D, when we actually have some human data for a D drug and the benefits of taking may outweigh the risk; the categories are rarely changed despite new evidence; a drug that may be a "D" in the first trimester is not necessarily contraindicated in later pregnancy and vice versa; an X drug may be so because it doesn't need to be used in pregnancy, such as statins. See for more info.