The Biogen Multiple Sclerosis Pregnancy Exposure Registry is a prospective, observational registry designed to evaluate pregnancy outcomes in women with multiple sclerosis (MS) who were exposed to a Registry-specified Biogen Multiple Sclerosis product during the eligibility window for that product. Women of childbearing potential are a considerable segment of the patient population affected by MS and are likely to be exposed to a Registry-specified Biogen MS product around the time of conception and during pregnancy. Biogen completed pregnancy registries for Avonex and Tysabri; however, formal studies in pregnant women have not been conducted. Therefore, it is important to evaluate, in a global Pregnancy Registry, how exposure to a marketed Biogen MS product specified in this Pregnancy Registry may affect pregnancy and infant outcomes. Data will be collected on prospective pregnancies (i.e. enrollment prior to knowledge of outcome) at time of enrollment, 6 to 7 months gestation, and approximately 4,12, and 52 weeks after estimated date of delivery. The prevalence of spontaneous abortions, birth defects, and other pregnancy and infant outcomes will be calculated and compared to background rates from external sources such as the European Surveillance of Congenital Anomalies.