Pregnancy and fetal outcomes following natalizumab exposure in pregnancy. A prospective, controlled observational study

Mult Scler. 2015 Feb;21(2):198-205. doi: 10.1177/1352458514546790. Epub 2014 Aug 26.


Background: Safety data on first-trimester natalizumab exposure are scarce, as natalizumab is usually withdrawn three months before pregnancy.

Objective: The objective of this paper is to investigate the fetal safety of exposure to natalizumab (Tysabri(®)) during the first trimester of pregnancy using disease-matched (DM) and healthy control (HC) comparison groups.

Methods: A total of 101 German women with RRMS exposed to natalizumab during the first trimester of pregnancy were identified. Birth outcomes in the exposed group were compared to a DM group (N = 78) with or without exposure to other disease-modifying drugs, and an HC group (N = 97).

Results: A total of 77, 69 and 92 live births occurred in the Exposed, DM and HC groups, respectively. The rates of major malformations (p = 0.67), low birth weight (<2500 grams) (p = 1.0) and premature birth (p = 0.37) did not differ among groups. Higher miscarriage rates (p = 0.002) and lower birth weights (p = 0.001) occurred among the Exposed and DM groups, as compared to the HC; however, there was no significant difference between the Exposed and DM groups.

Conclusion: Exposure to natalizumab in early pregnancy does not appear to increase the risk of adverse pregnancy outcomes in comparison to a DM group not exposed to natalizumab.

Keywords: Multiple sclerosis; fetal safety; natalizumab; pregnancy exposure.

Publication types

  • Observational Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Female
  • Humans
  • Immunologic Factors / adverse effects*
  • Infant, Newborn
  • Multiple Sclerosis, Relapsing-Remitting / drug therapy*
  • Natalizumab / adverse effects*
  • Pregnancy
  • Pregnancy Complications / drug therapy*
  • Pregnancy Outcome*
  • Pregnancy Trimester, First / drug effects


  • Immunologic Factors
  • Natalizumab