The primary objective(s) of the study is to evaluate the impact of exposure to SC Peginterferon beta-1a or IM Interferon beta-1a before and during pregnancy on pregnancy outcome in female participants who had registered in the German Patient Support Program (PSP) and of whom a pregnancy report and pregnancy outcome report is available.

The secondary objectives of this study are applicable for a subpopulation of the above-mentioned population, i.e. for participants of whom data on a standardized questionnaire collected during a telephone interview is available.

This is an observational study with focus on existing pregnancy reporting forms (retrospective part) and a patient's questionnaire which is completed at a single point of time (prospective part). Main data source for the retrospective data (from 2014 until December 2019) will be captured from multiple sclerosis service-center (MSSC) database, i.e. the entered pregnancy report (to be completed as soon as pregnancy becomes known) and pregnancy outcomes report (to be completed after completion of pregnancy).

Prospective data (December 2020 to 31 March 2021) will be captured as standardized ePDF questionnaire completed during telephone interview. If the pregnancy report or the pregnancy outcome report is incomplete, i.e. the data above was not collected, the open questions will be addressed during a telephone interview performed by the MSSC and the new information will be entered into the MSCC database. The patient questionnaire will be completed at a single point of time during the telephone interview performed by the MSSC.

Inclusion Criteria:

• Diagnosed relapsing-remitting multiple sclerosis (RRMS) or clinically isolated syndrome (CIS) (CIS indication only applicable for interferon beta-1a)
• Exposure to either SC Peginterferon beta-1a therapy or an IM Interferon beta-1a therapy before or during pregnancy
• Registered in the PSP of the multiple sclerosis service- center (MSSC) and agreed in writing to the privacy policy of the registration form
• Reported pregnancy data (pregnancy report and pregnancy outcome report) available at MSSC. Note: only pregnancy data (i.e. obtained until 15 October 2020) will be considered.
• Pregnancy outcome in the retrospectively collected data was a live birth

Exclusion Criteria: Any criteria that does not fulfil the above-mentioned inclusion criteria.

NOTE: Other protocol defined Inclusion criteria may apply

All female participants treated with SC Peginterferon beta-1a therapy or IM Interferon beta-1a therapy who fulfil the inclusion criteria are eligible to participate in the study.

In accordance with Biogen's Clinical Trial Transparency and Data Sharing Policy on https://www.biogentrialtransparency.com/