Drug Classification Schedule of Medicines During Pregnancy

hand holding a pill

To help pregnant women and their healthcare providers choose prescription and OTC drugs safely, the FDA created a drug schedule for pregnant women. It’s a grading system labeling drugs in categories from A (considered safest, with controlled human studies that have shown no fetal risks), through X (drugs that have proven fetal risks that outweigh any possible benefit). Letter categories are chosen based on what studies have shown about the medicine when used in pregnant women and animals. (The FDA is phasing out this system.)

Definition of medicine categories

Pregnancy Category: A

Definition: In human studies, pregnant women used the medicine and their babies did not have any problems related to using the medicine.

Examples of Drugs:

  • Folic acid
  • Levothyroxine (thyroid hormone medicine)

Pregnancy Category: B

Definition: In humans, there are no good studies. But in animal studies, pregnant animals received the medicine, and the babies did not show any problems related to the medicine.

Or

In animal studies, pregnant animals received the medicine, and some babies had problems. But in human studies, pregnant women used the medicine and their babies did not have any problems related to using the medicine.

Examples of Drugs:

  • Some antibiotics like amoxicillin.
  • Zofran (ondansetron) for nausea
  • Glucophage (metformin) for diabetes
  • Some insulins used to treat diabetes such as regular and NPH insulin.

Pregnancy Category: C

Definition: In humans, there are no good studies. In animals, pregnant animals treated with the medicine had some babies with problems. However, sometimes the medicine may still help the human mothers and babies more than it might harm.

Or

No animal studies have been done, and there are no good studies in pregnant women.

Examples of Drugs:

  • Diflucan (fluconazole) for yeast infections
  • Ventolin (albuterol) for asthma
  • Zoloft (sertraline) and Prozac (fluoxetine) for depression

Pregnancy Category: D

Definition: Studies in humans and other reports show that when pregnant women use the medicine, some babies are born with problems related to the medicine. However, in some serious situations, the medicine may still help the mother and the baby more than it might harm.

Examples of Drugs:

  • Paxil (paroxetine) for depression
  • Lithium for bipolar disorder
  • Dilantin (phenytoin) for epileptic seizures
  • Some cancer chemotherapy

Pregnancy Category: X

Definition: Studies or reports in humans or animals show that mothers using the medicine during pregnancy may have babies with problems related to the medicine. There are no situations where the medicine can help the mother or baby enough to make the risk of problems worth it. These medicines should never be used by pregnant women.

Examples of Drugs:

  • Accutane (isotretinoin) for cystic acne
  • Thalomid (thalidomide) for a type of skin disease

The FDA is changing prescription medicine label information and the pregnancy part of the label will change over the next few years. As this prescription information is updated, it is added to an online information clearinghouse from the NIH and the US National Library of Medicine called DailyMed that gives up-to-date, free information to consumers and health care providers.


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