Pregnancy category

The pregnancy category of a pharmaceutical agent is an assessment of the risk of foetal injury due to the pharmaceutical, if it is used as directed by the mother during pregnancy. It does not include any risks conferred by pharmaceutical agents or their metabolites that are present in breast milk.

United States
In 1979, the United States Food and Drug Administration (FDA) introduced a classification of foetal risks due to pharmaceuticals. This was based on a similar system that was introduced in Sweden just one year earlier.

The United States FDA has the following definitions for the pregnancy categories:

One characteristic of the FDA definitions of the pregnancy categories is that the FDA requires a relatively large amount of high-quality data on a pharmaceutical for it to be defined as Pregnancy Category A. As a result of this, many drugs that would be considered Pregnancy Category A in other countries are allocated to Category C by the FDA.

Australia
Australia has a slightly different pregnancy category system from the United States - notably the subdivision of Category B. The system, as outlined below, was established by the Congenital Abnormalities Sub-committee of the Australian Drug Evaluation Committee (ADEC).

The subcategorisation of Category B, while offering additional information which may be of benefit in evaluating the risk vs benefit, presents its own problem of data reliability - since human data is lacking or inadequate, the subcategorisation is based on animal data. Furthermore, allocation of a drug in Category B does not necessarily imply greater safety than Category C.

Drugs in Category D are not absolutely contraindicated in pregnancy, unlike Category X. In some cases Category D was assigned to a drug on the basis of suspicion.

Categorisation of selected agents
The data presented is for comparative and illustrative purposes only, and may have been superseded by updated data.