Study Examines Pregnancy Outcomes for Patients on Natalizumab

Patients who are taking it and are pregnant or plan to become pregnant “are currently advised to balance the potential benefits and potential risks of exposure when considering treatment options,” say the authors.

Natalizumab does not appear to cause a malformations or spontaneous abortions according to an observational study. The study, which was based on the Tysabri Pregnancy Exposure Registry, (TPER, or the Registry) was conducted by Susan Friend, of Biogen, Innovation House, and colleagues, and was published in BMC Neurology.

Natalizumab is used to treat multiple sclerosis (MS) and Crohn’s disease (CD). Patients who are taking it and are pregnant or plan to become pregnant “are currently advised to balance the potential benefits and potential risks of exposure when considering treatment options,” say the authors. “This study,” they say, “prospectively evaluated pregnancy outcomes of women with MS or CD who were exposed to natalizumab within the 3 months before conception or during pregnancy.”

The TPER was a global registry and follow-up study. The researchers say, “The Registry collected information routinely documented in the patient and infant medical record with no Registry-required interventions or procedures conducted.” The information was gathered between February 14, 2007 and April 24, 2011, and a total of 369 patients with MS and 7 with CD were enrolled. Of those 355 had known pregnancy outcomes.

The researchers report that “57 birth defects (minor or major) were confirmed in 30 infants (including 3 sets of twins); of these 29 were live births and 1 was an elective termination resulting from a birth defect.” There were 32 spontaneous abortions, and one stillbirth. When compared with the Metropolitan Atlanta Congenital Defects Program (MACD) classification, “the rate of reported birth defects in the infants of women exposed to natalizumab during pregnancy was higher” by 2.67% say the researchers, adding, “No specific pattern of malformations was seen within the observed birth defects.”

Although there was no specific pattern of malformations, and the rate of spontaneous abortion among women exposed to natalizumab was the same as that of women in the general population, the authors say, “The potential influence of natalizumab exposure at different gestational time points should be considered.”

The Registry did not include many reports of women exposed to natalizumab later in their pregnancies, but “a recent case series of 13 pregnancies in women with aggressive MS observed hematological abnormalities in 10 of 13 newborns following third-trimester exposure,” say the researchers.

The researchers conclude, “The natalizumab prescribing information indicates that natalizumab should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus; although the Registry has noted limitations and more research is needed, the findings from the Registry may be informative to clinicians and patients in weighing potential risks and benefits of natalizumab exposure during pregnancy.”

Further MS Reading:

Clinician and Patient Preferences, Risk Tolerance Guide Relapsing Multiple Sclerosis Treatment Strategies

Multiple Sclerosis and Progressive Multifocal Leukoencephalopathy: Risks and Detection

Talking to Patients about Their Multiple Sclerosis