Pregnancy category

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The pregnancy category of a pharmaceutical agent is an assessment of the risk of fetal 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 in breast milk.

Every drug has specific information listed in its product literature. In the UK, while no preset categories are applied, the British National Formulary gives a table of drugs to be avoided or used with caution in pregnancy, and does so using a limited number of key phrases.[1]

United States[edit]

In 1979, the United States Food and Drug Administration (FDA) introduced a classification of fetal risks due to pharmaceuticals. This was based on a similar system that was introduced in Sweden one year earlier. The same guidelines are followed in India as well.

Pregnancy Category Description
A No risk in controlled human studies: Adequate and well-controlled human studies have failed to demonstrate a risk to the fetus in the first trimester of pregnancy (and there is no evidence of risk in later trimesters).
B No risk in other studies: Animal reproduction studies have failed to demonstrate a risk to the fetus and there are no adequate and well-controlled studies in pregnant women OR Animal studies have shown an adverse effect, but adequate and well-controlled studies in pregnant women have failed to demonstrate a risk to the fetus in any trimester.
C Risk not ruled out: Animal reproduction studies have shown an adverse effect on the fetus and there are no adequate and well-controlled studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks.
D Positive evidence of risk: There is positive evidence of human fetal risk based on adverse reaction data from investigational or marketing experience or studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks.
X Contraindicated in Pregnancy: Studies in animals or humans have demonstrated fetal abnormalities and/or there is positive evidence of human fetal risk based on adverse reaction data from investigational or marketing experience, and the risks involved in use of the drug in pregnant women clearly outweigh potential benefits.
N FDA has not yet classified the drug into a specified pregnancy category.

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. See below.

The FDA has proposed updating its approach to labeling.[2] Rather than assigning drugs to categories, there is a narrative description of the evidence available for use of the drug in pregnancy.[3]

Australia[edit]

Australia has a slightly different pregnancy category system[4] from the United States - notably the subdivision of Category B. The system, as outlined below, was developed by medical and scientific experts based on available evidence of risks associated with taking particular medicines while pregnant.

Australian categorisation system for prescribing medicines in pregnancy
Pregnancy Category A Drugs which have been taken by a large number of pregnant women and women of childbearing age without an increase in the frequency of malformations or other direct or indirect harmful effects on the fetus having been observed.
Pregnancy 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.
Pregnancy 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.
Pregnancy 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.
Pregnancy Category C Drugs which, owing to their pharmaceutical 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.
Pregnancy 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.
Pregnancy 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.

Germany[edit]

Category Description
Gr 1 Extensive human tests and animal studies have not shown the drug to be embryotoxic/teratogenic.
Gr 2 Extensive human tests of the drug have not shown the drug to be embryotoxic/teratogenic.
Gr 3 Extensive human tests of the drug have not shown the drug to be embryotoxic/teratogenic. However, the drug appears to be embryotoxic/teratogenic in animals.
Gr 4 No adequate and well-controlled studies of the drug's effects on humans are available. Animal studies have shown no embryotoxic/teratogenic effects.
Gr 5 No adequate and well-controlled studies of the drug's effects on humans are available.
Gr 6 No adequate and well-controlled studies of the drug's effects on humans are available. Animal studies have shown embryotoxic/teratogenic effects.
Gr 7 There is a risk that the drug is embryotoxic / teratogenic in humans, at least in the first trimester.
Gr 8 There is a risk that the drug is toxic to fetuses throughout the second and third trimesters.
Gr 9 There is a risk that the drug causes prenatal complications or abnormalities.
Gr 10 There is a risk that the drug causes hormone specific action on the human fetus.
Gr 11 There is a known risk that the drug is a mutagen/carcinogen.

Categorization of selected agents[edit]

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

Classification of some agents, based on different national bodies
Pharmaceutical agent Australia United States
Acetaminophen/Paracetamol A C
Acetylsalicylic acid/Aspirin C D third trimester
Amoxicillin A B
Amoxicillin with clavulanic acid B1 B
Cefotaxime B1 B
Diclofenac C D third trimester
Isotretinoin X X
Leflunomide X X
Loperamide B3 C
Paroxetine D D
Phenytoin D D
Rifampicin C C
Thalidomide X X
Theophylline A C
Temazepam C X
Tetracycline D D
Triamcinolone (skin) A C

Notes[edit]

  1. ^ "Appendix 4: Pregnancy". British National Formulary (55 ed.). March 2008. [incomplete short citation]
  2. ^ "Federal Register /Vol. 73, No. 104 /Thursday, May 29, 2008 / Proposed Rules". Archived from the original on 2012-09-16. Retrieved 2014-02-13. 
  3. ^ Wood, Wende. "FDA pregnancy categories: help or hindrance?". College of Psychiatric & Neurologic Pharmacists. Retrieved 3 March 2014. 
  4. ^ "Australian categorisation system for prescribing medicines in pregnancy". Therapeutic Goods Administration. Retrieved 16 April 2014. 

References[edit]