Experts have developed an Australian system for prescribing medicines in pregnancy. They have grouped medicines into categories (A, B1, B2, B3, C, D and X) based on evidence of risk to the unborn baby.
This system is the basis for our Prescribing medicines in pregnancy database.
The prescribing in pregnancy database is for healthcare professionals who treat pregnant women. It is not for public use or a substitute for professional medical advice.
The use of any medicine in pregnancy should consider both the risks and benefits to the mother and baby.
Deciding to take a medicine during pregnancy should:
- involve a health professional and the patient
- consider all the available information on the medicine
- consider the patient’s specific circumstances.
What does the Australian categorisation system consider?
Most medicines can affect the baby during pregnancy. Harm includes birth defects, unwanted pharmacological effects and other problems later in life.
The system does not account for rare and unexpected reactions the unborn baby might have to a medicine.
The categories might not apply in situations such as:
- overdose
- occupational exposure
- other situations where the patient exceeds the recommended therapeutic dose.
Some medicines are in more than one category. This is because a mother’s exposure and risk can vary, depending on:
- dose
- route of administration
- dosing regimen.
For example, using a medication at a low dose, or for a short while, or topically, may be of low risk to an unborn baby. Yet, the same medication may be harmful if used long term, for another condition, or given orally.
How the Australian categorisation system works
The Australian system for categorising medicines in pregnancy uses an alphabetical structure. However, this does not always mean categories that come first in alphabetic order are safer.
For example, medicines in category C may not be potentially more harmful to the unborn baby than drugs in Category B.
As a broad guide:
- We use category B where human evidence (or data) is lacking or inadequate.
- The B subcategories (B1, B2, and B3) are based on animal data.
- A medicine given a B category does not imply greater safety than a C category.
- Medicines in category D are not absolutely contraindicated during pregnancy.
- For medicines with more than one ‘active’ ingredient (as opposed to inactive ingredients, or fillers), we base the category on the single ‘active’ ingredient posing the greatest risk to the unborn baby.
Due to legal considerations in Australia, sponsor companies may apply a more restrictive category to their medicine than the available data justifies.
The pregnancy category and safety statement for some medicines that are no longer registered for use in Australia are presented in this database for information only.
Definitions of the Australian categories for prescribing medicines in pregnancy
Category A
Drugs which have been taken by a large number of pregnant women and women of childbearing age without any proven increase in the frequency of malformations or other direct or indirect harmful effects on the fetus having been observed.
Category B1
Drugs which have been taken by only a limited number of pregnant women and women of childbearing age, without an increase in the frequency of malformation or other direct or indirect harmful effects on the human fetus having been observed.
Studies in animals have not shown evidence of an increased occurrence of fetal damage.
Category B2
Drugs which have been taken by only a limited number of pregnant women and women of childbearing age, without an increase in the frequency of malformation or other direct or indirect harmful effects on the human fetus having been observed.
Studies in animals are inadequate or may be lacking, but available data show no evidence of an increased occurrence of fetal damage.
Category B3
Drugs which have been taken by only a limited number of pregnant women and women of childbearing age, without an increase in the frequency of malformation or other direct or indirect harmful effects on the human fetus having been observed.
Studies in animals have shown evidence of an increased occurrence of fetal damage, the significance of which is considered uncertain in humans.
Category C
Drugs which, owing to their pharmacological effects, have caused or may be suspected of causing, harmful effects on the human fetus or neonate without causing malformations. These effects may be reversible. Accompanying texts should be consulted for further details.
Category D
Drugs which have caused, are suspected to have caused or may be expected to cause, an increased incidence of human fetal malformations or irreversible damage. These drugs may also have adverse pharmacological effects. Accompanying texts should be consulted for further details.
Category X
Drugs which have such a high risk of causing permanent damage to the fetus that they should not be used in pregnancy or when there is a possibility of pregnancy.
More information
To access the database for prescribing medicines in pregnancy, see the Prescribing medicines in pregnancy database.
For therapeutic goods exempt from the Australian categorisation system for prescribing in pregnancy see Therapeutic goods exempted from pregnancy categorisation.
For the latest updates to the Prescribing in pregnancy database see our news articles.