How is the risk of neurologic medications during pregnancy determined?

Updated: Aug 20, 2019
  • Author: Carmel Armon, MD, MSc, MHS; Chief Editor: Stephen A Berman, MD, PhD, MBA  more...
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At least 2 systems are used to classify the risk associated with specific medications: the US Food and Drug Administration (FDA) system and the automated Teratogen Information System (TERIS). [4, 5] The FDA risk categories are as follows:

  • Category A - Controlled human studies show no risk

  • Category B – There is no evidence of risk in humans, but no controlled human studies are documented

  • Category C - Risk to humans has not been excluded

  • Category D – There is positive evidence of risk to humans from human or animal studies

  • Category X - Contraindicated in pregnancy

Unfortunately, the correlation between the 2 risk classification systems is poor. According to the TERIS, the teratogenic risk in human pregnancy is undetermined for 91.2% of the drug treatments approved in the United States between 1980 and 2000.

For most drug treatments introduced in the past 2-3 decades, the information available to pregnant women and their physicians is insufficient to determine whether the benefits exceed the teratogenic risks. Therefore, in most cases, the cautionary approach (category C) is based on an absence of information, and individualized discussions between the woman and her treating physicians are required to permit an informed joint decision.

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