USA Drug Categories

From Embryology

USA FDA Fetal Risk Categories

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In the United States the government Food and Drug Administration (FDA) has established the following drug classification. See also Australian Drug Categories

FDA September 2014 - Discussion - anesthetic drugs to infants and young children

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Some Recent Findings

  • Recent changes in pregnancy and lactation labeling: retirement of risk categories[1] "The rapid development and increased availability of novel pharmacologic therapies and pharmaceutical products has amplified the potential for drug exposure during pregnancy. Many drugs are beneficial for disease state management during pregnancy and provide significant fetal and maternal health benefits. However, a paucity of safety data combined with the imprecision of the current risk category system renders risk versus benefit assessment difficult. In response to decades of criticism, the U.S. Food and Drug Administration (FDA) is implementing a new pregnancy and lactation labeling rule designed to improve risk versus benefit assessment of drugs used in pregnant and nursing mothers. These recommendations will provide clear and detailed information for both patients and health care providers, and they will include three main categories: risk summary, clinical considerations, and data. The new labeling rules remove the previous letter risk categorization system (A, B, C, D, X). In this review, we summarize the upcoming FDA labeling changes and discuss their potential consequences on clinical practice."
  • Obstetric toxicology: teratogens[2] "The emergency physician frequently encounters women who seek care because of pregnancy- and nonpregnancy-related complaints. Many medications are safe for use during pregnancy, including several that are listed as potential teratogens based on the Food and Drug Administration's (FDA) pregnancy classification; but it is important that the emergency physician know and recognize which drugs can be given in pregnancy and which drugs are absolutely contraindicated. Expert resources should be identified and used because the FDA's classification of drugs based on pregnancy risk does not represent the most up-to-date or accurate assessment of a drug's safety."
More recent papers
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This table shows an automated computer PubMed search using the listed sub-heading term.

  • Therefore the list of references do not reflect any editorial selection of material based on content or relevance.
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References listed on the rest of the content page and the associated discussion page (listed under the publication year sub-headings) do include some editorial selection based upon both relevance and availability.

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Search term: tFDA Fetal Risk Category

Mary Regina Boland, Fernanda Polubriaginof, Nicholas P Tatonetti Development of A Machine Learning Algorithm to Classify Drugs Of Unknown Fetal Effect. Sci Rep: 2017, 7(1);12839 PubMed 28993650

Fantahun Molla, Admassu Assen, Solomon Abrha, Birhanetensay Masresha, Arega Gashaw, Abrham Wondimu, Yared Belete, Wondim Melkam Prescription drug use during pregnancy in Southern Tigray region, North Ethiopia. BMC Pregnancy Childbirth: 2017, 17(1);170 PubMed 28583106

Naichaya Chamroonkul, Teerha Piratvisuth Hepatitis B During Pregnancy in Endemic Areas: Screening, Treatment, and Prevention of Mother-to-Child Transmission. Paediatr Drugs: 2017; PubMed 28434087

Abiodun Idowu Adanikin, Jacob Olumuyiwa Awoleke Antenatal drug consumption: the burden of self-medication in a developing world setting. Trop Doct: 2016; PubMed 27302199

Jessica Ansari, Brendan Carvalho, Steven L Shafer, Pamela Flood Pharmacokinetics and Pharmacodynamics of Drugs Commonly Used in Pregnancy and Parturition. Anesth. Analg.: 2016, 122(3);786-804 PubMed 26891392

Category A

Controlled studies in women fail to demonstrate a risk to the fetus in the first trimester, there is no evidence of a risk in later trimesters, and the possibility of fetal harm appears remote.

Category B

Either animal reproduction studies have not demonstrated a fetal risk but there are no controlled studies in pregnant women, or animal reproduction studies have shown on adverse effect (other than a decrease in fertility) that was not confirmed in controlled studies in women in the first trimester (and there is no evidence of risk in later trimesters).

Category C

Either studies in animals have revealed adverse effects on the fetus (teratogenic or embryocidal or other) and there are no controlled studies in women, or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the fetus.

Category D

There is positive evidence of human fetal risk, but the benefits from use in pregnant women may be acceptable despite the risk (eg, if the drug is needed in a life-threatening situation or for a serious disease for which safer drugs cannot be used or are ineffective).

Category X

Studies in animals or human beings have demonstrated fetal abnormalities or there is evidence of fetal risk based on human experience or both, and the risk of use of the drug in pregnant women clearly outweighs any possible benefit. The drug is contraindicated in women who are or may become pregnant.


  1. Leda L Ramoz, Nima M Patel-Shori Recent changes in pregnancy and lactation labeling: retirement of risk categories. Pharmacotherapy: 2014, 34(4);389-95 PubMed 24390829
  2. Michael Levine, Ayrn D O'Connor Obstetric toxicology: teratogens. Emerg. Med. Clin. North Am.: 2012, 30(4);977-90 PubMed 23137407

Search PubMed: US Drug Categories | Drug Categories | teratogenic drugs

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Cite this page: Hill, M.A. 2018 Embryology USA Drug Categories. Retrieved January 16, 2018, from

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