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Does Interferon Beta Affect Pregnancy?

Conflicting findings from two studies suggest this complex issue is still unfolding.

Multiple sclerosis (MS) has a female preponderance and affects people during their reproductive years. Thus, evaluating the reproductive effects of interferon beta (IFN-ß), a commonly used therapy for MS, is clinically important. Two recent reports attempt to address this issue.

Sandberg-Wollheim and colleagues reviewed individual patient data from eight recent clinical trials of IFNß-1a (5 placebo-controlled with active-drug extension phases of variable duration). Of 69 pregnancies reported, 41 occurred in patients who were receiving IFNß-1a at conception or who had discontinued IFNß-1a within 2 weeks before conception (in-utero–exposure group). Twenty-two pregnancies were reported in patients who had discontinued IFNß-1a therapy more than 2 weeks before conception (previous-exposure group), and six pregnancies occurred in patients receiving placebo (placebo group). In the in-utero–exposure group, 26% of viable pregnancies (8 of 31) ended in spontaneous abortions and 3.2% in fetal death (1 of 31), proportions considered to be within the expected estimate for an equal-sized, randomly selected group from the general population. IFNß-1a did not appear to affect pregnancy outcomes, and there was no evidence of teratogenesis.

Boskovic and colleagues conducted a longitudinal, controlled, cohort study of pregnant women who contacted a teratogen information and counseling service between 1997 and 2004 regarding maternal IFN-ß or glatiramer acetate exposure during pregnancy. They compared outcomes among three groups: 16 women who used beta interferon during 23 pregnancies (study group; mean gestational exposure to IFN-ß therapy, 9 weeks; range, 2–38 weeks), those who discontinued IFN-ß or glatiramer acetate before conception (disease-matched group), and callers to a pregnancy nausea and vomiting helpline (healthy control group). Mothers in the study group were a significant 6.9 times more likely than the other mothers to produce a non-live birth, after controlling for maternal age, gravidity, and prior pregnancy. In addition, interferon had an independent and significant negative effect on birth weight.

Comment: Both of these studies suffer from having small numbers of participants and potentially confounding methodologic issues. In the Boskovic study, the duration of in utero exposure to IFN-ß was longer than in the Sandberg-Wollheim study, reflecting perhaps that the subjects in the latter study were part of a clinical trial. This might explain why one study found adverse effects and the other did not, although other confounding variables make a definitive conclusion difficult. However, given that studies in primates showed increased abortion rates with IFN-ß exposure, and that the Boskovic study raises suspicion of similar adverse effects in humans, clinicians should continue counseling patients to stop IFN-ß before attempting pregnancy.

— Samia Khoury, MD

Dr. Khoury is Associate Professor of Neurology, Harvard Medical School, and Co-Director of the Partners MS Center, Brigham and Women's Hospital, Boston.

Published in Journal Watch Neurology November 28, 2005

Citation(s):

Sandberg-Wollheim M et al. Pregnancy outcomes during treatment with interferon beta-1a in patients with multiple sclerosis. Neurology 2005 Sep 27; 65:802-6.

• Original article (Subscription may be required)
• Medline abstract (Free)

Boskovic R et al. The reproductive effects of beta interferon therapy in pregnancy: A longitudinal cohort. Neurology 2005 Sep 27; 65:807-11.

• Original article (Subscription may be required)
• Medline abstract (Free)