Pregnancy outcomes in patients treated with leflunomide, the parent compound of the multiple sclerosis drug teriflunomide

Reprod Toxicol. 2020 Aug:95:45-50. doi: 10.1016/j.reprotox.2020.04.073. Epub 2020 May 11.


Leflunomide is contraindicated in pregnant women, yet human data from leflunomide-exposed pregnancies do not indicate an embryofetal toxicity signal. The objective of the present analysis was to report pregnancy outcomes for leflunomide-exposed pregnancies in clinical trials and in the post-marketing setting. Pregnancy outcomes are summarized from leflunomide clinical trials and the post-marketing setting. The data cut-off was 31 December 2017. Of 1167 pregnancies reported in female patients exposed to leflunomide, 587 had a known outcome. Of these, 337 (57.4%) were reported prospectively and 250 (42.6%) were reported retrospectively. Of the 587 pregnancies with a known outcome (which involved 15 sets of twins), there were 333 (56.7%) live births, with 285 (48.6%) full-term births and 48 (8.2%) pre-term births. Birth defects were reported in 44 babies/fetuses/embryos from 587 pregnancies, with 2 reporting at least 3 minor defects and 20 reporting major defects. Major defects were reported in 3 of 337 (0.9%) prospectively-reported pregnancies; 1 major birth defect occurred in a live birth, and 2 were electively terminated due to a detected fetal anomaly. Two of the babies/fetuses/embryos, a live birth and an electively aborted baby/fetus/embryo, from 206 prospectively-reported pregnancies exposed to leflunomide during the first trimester experienced major defects. Birth defects showed no specific patterns and were distributed evenly across organ systems. Outcomes were consistent with the general population. These findings do not suggest an embryofetal toxicity signal for leflunomide, which is consistent with previous findings from leflunomide-exposed pregnancies.

Keywords: Embryofetal toxicity; Leflunomide; Neurology; Pregnancy; Teriflunomide.

MeSH terms

  • Adult
  • Congenital Abnormalities / epidemiology*
  • Crotonates
  • Female
  • Humans
  • Hydroxybutyrates
  • Immunosuppressive Agents / therapeutic use*
  • Leflunomide / therapeutic use*
  • Multiple Sclerosis
  • Nitriles
  • Pregnancy
  • Pregnancy Outcome / epidemiology*
  • Toluidines
  • Young Adult


  • Crotonates
  • Hydroxybutyrates
  • Immunosuppressive Agents
  • Nitriles
  • Toluidines
  • teriflunomide
  • Leflunomide