This national registry is the largest study to date to focus exclusively on the effects of intramuscular interferon beta-1a exposure in women with multiple sclerosis who are pregnant.

Results from this national registry suggest that intramuscular interferon beta-1a exposure within ~ 1 week of conception or during the first trimester of pregnancy is not clinically associated with adverse pregnancy outcomes.

Rates of spontaneous abortion were consistent with previous findings and no patterns of birth defects suggestive of an unusual distribution were observed.