Women diagnosed with multiple sclerosis who become pregnant should stay off therapy with interferon interferon until delivery, according to a group of doctors who published a paper recently on the topic in the medical literature.1 There aren't necessarily any risks associated with this form of treatment for pregnant women, though limited information from animal studies has suggested that the medication may boost the risk of miscarriage, stated the researchers who had taken part in an international study. However, there isn't enough information for physicians to assure their patients of the safety of the therapy during pregnancy, they wrote.
The study was published online at the website of the journal Neurology in August.
"Although patients with multiple sclerosis (MS) are advised to stop interferon beta-1a therapy before becoming pregnant, some patients become pregnant while on treatment," wrote the study team headed by Magnhild Sandberg-Wollheim, MD, PhD, a neurologist at University Hospital in Lund, Sweden.
Attempts to Find Consistent Data
There are two brands of interferon beta-1a available to people with multiple sclerosis. Avonex (Biogen Idec) is an intramuscular (IM) injection therapy designed to slow the progression of physical disability, lower the number of MS relapses, and reduce the number of active brain lesions in people with relapsing-remitting MS.2 The other interferon beta-1a medication available is marketed as Rebif (Serono/Pfizer). It is a subcutaneous (given under the skin) injection therapy for people with relapsing MS, and is designed to ease the frequency of disease exacerbations and delay the progression to disability.3
There has been insufficient information about the effects of interferon treatment in pregnancy, particularly about whether it increases the risk of miscarriage. Animal studies have found higher-than-expected miscarriage rates linked to interferon-beta-1a use, but the results have been conflicting. Thus, women are advised to stop taking the medication, at least to be on the safe side. "We tell them to stop treatment with Interferon beta before they become pregnant since we do not know for sure that the treatment does no harm to the fetus," Sandberg-Wollheim told Priority Healthcare. "So, these patients have to make a decision to stop medication and take into account that they will be without treatment for a period of uncertain length before they become pregnant."
Thus, in hopes of answering their questions about this topic, Sandberg-Wollheim's team went back into the medical literature to find relevant studies.
Past Studies Reviewed
The team reviewed the results of eight clinical trials conducted between 1994 and 2003 that evaluated interferon beta-1a (Avonex or Rebif) in this way. Of more than 3,300 women who had taken part in these trials, 69 were pregnant. Of those, 41 women were taking interferon beta-1a or had stopped receiving the medication within two weeks prior to conception. Twenty-two of the 69 pregnant women had stopped taking the medicine more than two weeks prior to conception. Six patients had taken a placebo, an intervention with no medicinal value used as a comparison in clinical trials.
In the group of 41 women who were taking interferon beta-1a or had stopped taking it within two weeks of their pregnancy, Sandberg-Wollheim's group discovered there were 20 healthy deliveries, one healthy premature infant, nine abortions, eight miscarriages, one fetal death, and one infant with a birth defect (hydrocephalus). Information on one additional patient was not available.
The fetal death had occurred after 22 weeks of pregnancy, and followed an infection that occurred after an amniocentesis. The mother had halted interferon beta-1a therapy about one week after conception.
Miscarriage Risk Was Generally the Same
In conclusion, while the rates of miscarriage associated with interferon beta-1a use in this analysis were higher compared to what might be expected among the general population, the differences were not significant, Sandberg-Wollheim and his team wrote. "The overall rate of pregnancy loss was 16% of all pregnancies that could potentially go full term, all occurring in pregnancies exposed to interferon beta-1a," they wrote. "[By comparison, miscarriage] is estimated to occur in 15% to 20% of pregnancies."
Additionally, the majority of women who took part in these clinical trials had successful pregnancies, despite receiving interferon beta-1a at some point during or prior to conception, and even previous prolonged exposure to the medicine had no significant impact.
As a result, due to the continuing lack of clear evidence about the effect of interferon beta-1a on the course of pregnancy, "patients should still be advised to discontinue interferon beta-1a prior to planned pregnancy or if they become pregnant," the research team concluded.
Going forward, Sandberg-Wollheim stressed that "it is very important" to continue collecting data on the effect of interferon beta on pregnancy, given the limited information currently available. One such data collection effort involves a registry maintained by the maker of Rebif, which Sandberg-Wollheim and other experts continuously monitor.
1. Sandberg-Wollheim M, Frank D, Goodwin TM et al. Pregnancy outcomes during treatment with interferon beta-1a in patients with multiple sclerosis. Neurology 2005 Aug 10;[Epub ahead of print].
2. Biogen Idec. Starting on Avonex. Available at: http://www.avonex.com/msavProject/avonex.portal
/_baseurl/threeColLayout/SCSRepository/en_US/avonex/home/
starting_on_avonex/index.xml. Accessed September 23, 2005.
3. Serono/Pfizer. Rebif Prescribing Information. Available at: http://www.rebif.com/assets/pdfs/Rebif_PI.pdf. Accessed September 23, 2005.
John Martin is a long-time health journalist and an editor for Priority Healthcare. His credits include overseeing health news coverage for the website of Fox Television's The Health Network, and articles for the New York Post and other consumer and trade publications.
