New Safety Data on Pregnancy Outcomes in Women with MS Using Interferon Beta, Including Rebif®, Before and During First Trimester

Not intended for media based in the UK or U.S.

  • Data from a large population-based observational study in pregnant women with multiple sclerosis (MS) presented at the European Academy of Neurology (EAN) 2019 Congress
  • Data showed no difference in the risk of miscarriage and ectopic pregnancy in pregnant women with MS exposed to interferon beta, including Rebif®(subcutaneous interferon beta-1a), compared to unexposed pregnancies
  • Two-thirds of the 2.3 million people that have MS worldwide are women, most of them first diagnosed during the age of 25-35i when many are planning to start a family


DARMSTADT, Germany--()--Merck, a leading science and technology company, today announced that new pregnancy outcomes data in women with MS treated with interferon beta (IFN β), including Rebif® (interferon beta-1a), were presented at the European Academy of Neurology (EAN) 2019 Congress in Oslo, Norway. Results from the largest population-based observational study in women treated with IFN β who become pregnant showed no increase in the risk of miscarriage or ectopic pregnancy compared to those unexposed. The results are based on Finnish and Swedish health register data collected between 1996-2014.

“MS predominantly affects women in their 20`s and 30`s, when many are considering starting a family. Knowing what might happen if exposed to a disease-modifying treatment during pregnancy is extremely important,” said Professor Kerstin Hellwig, Department of Neurology at St. Josef Hospital, Germany. “These results provide important information for women with MS.”

In 2444 pregnancies with known outcomes, of which 797 pregnancies were exposed to interferon beta and 1647 pregnancies had no exposure, 8.3% (95% confidence interval [CI], 6.5–10.4) of the IFNβ-exposed and 12.0% (95% CI, 10.4–13.6) of the unexposed had spontaneous abortion, with no statistical difference between the groups (risk ratio [RR] 1.14; 95% CI 0.94–1.38). The prevalence of ectopic pregnancy was 1.6% (95% CI, 0.9–2.8) among IFNβ-exposed versus 3.2% (95% CI, 2.4–4.2) among the unexposed. A numerically decreased risk (RR 0.91; 95% CI, 0.52–1.61) was observed among the IFNβ-exposed, compared to those unexposed. Observational studies in general have inherent methodologic limitations that may generate bias and confounding.

In the EU, the initiation of Rebif® during pregnancy is currently contraindicated by the European Medicines Agency (EMA), see section 4.3 and 4.6 in the EU Summary of Product Characteristics (SMPC) for Rebif®. Merck has submitted regulatory filings with different health authorities to include safety data from these interferon registries in the Rebif® label. There is no guarantee that the use of interferon beta during pregnancy will be approved by any health authority worldwide.

“Our company has long been committed to providing treatment options and addressing the unmet needs of the MS patient community. The results of this study augment our knowledge of the benefits and risks of Rebif gathered over more than two decades,” said Dr. Maria Rivas, Chief Medical Officer at Merck.

All Merck Press Releases are distributed by e-mail at the same time they become available on the Merck Website. Please go to to register online, change your selection or discontinue this service.

About Rebif®

Rebif® (interferon beta-1a) is a disease-modifying drug used to treat relapsing forms of multiple sclerosis (MS) and is similar to the interferon beta protein produced by the human body. The efficacy of Rebif® in chronic progressive MS has not been established. Interferon ß is thought to help reduce inflammation. The exact mechanism is unknown.

Rebif®, which was approved in Europe in 1998 and in the US in 2002, is registered in more than 90 countries worldwide. Rebif® has been proven to delay the progression of disability, reduce the frequency of relapses and reduce MRI lesion activity and area.

Rebif® can be administrated with the RebiSmart® electronic auto-injection device (not approved in the US), or with the RebiDose® single-use disposable pen, or the manual multidose injection pen RebiSlide™. Rebif® can also be administered with the autoinjector Rebiject II® or by manual injection using ready-to-use pre-filled syringes. These injection devices are not approved in all countries.

In January 2012, the European commission approved the extension of the indication of Rebif® in early multiple sclerosis. The extension of the indication of Rebif® has not been submitted in the United States.

Rebif® should be used with caution in patients with a history of depression, liver disease, thyroid abnormalities and seizures. Most commonly reported side effects are flu-like symptoms, injection site disorders, elevation of liver enzymes and blood cell abnormalities. Patients, especially those with depression, seizure disorders, or liver problems, should discuss treatment with Rebif® with their doctors.

About Multiple Sclerosis

Multiple sclerosis (MS) is a chronic, inflammatory condition of the central nervous system and is the most common non-traumatic, disabling neurological disease in young adults. It is estimated that approximately 2.3 million people have MS worldwide. While symptoms can vary, the most common symptoms of MS include blurred vision, numbness or tingling in the limbs and problems with strength and coordination. The relapsing forms of MS are the most common.

Merck in Neurology and Immunology

Merck has a long-standing legacy in neurology and immunology, with significant R&D and commercial experience in multiple sclerosis (MS). The company`s current MS portfolio includes two products for the treatment of relapsing MS, with a robust pipeline focusing on discovering new therapies that have the potential to modulate key pathogenic mechanisms in MS. Merck aims to improve the lives of those living with MS, by addressing areas of unmet medical needs.

About Merck

Merck, a leading science and technology company, operates across healthcare, life science and performance materials. Around 52,000 employees work to make a positive difference to millions of people’s lives every day by creating more joyful and sustainable ways to live. From advancing gene editing technologies and discovering unique ways to treat the most challenging diseases to enabling the intelligence of devices – the company is everywhere. In 2018, Merck generated sales of € 14.8 billion in 66 countries.

Scientific exploration and responsible entrepreneurship have been key to Merck’s technological and scientific advances. This is how Merck has thrived since its founding in 1668. The founding family remains the majority owner of the publicly listed company. Merck holds the global rights to the Merck name and brand. The only exceptions are the United States and Canada, where the business sectors of Merck operate as EMD Serono in healthcare, MilliporeSigma in life science, and EMD Performance Materials.



Tone Brauti Fritzen
Phone: +49 151 1454 2694


Tone Brauti Fritzen
Phone: +49 151 1454 2694