Outcomes of pregnancy during interferon beta-1a therapy in Japanese patients with multiple sclerosis: Interim results of a postmarketing surveillance study

Objectives To evaluate pregnancy outcomes in Japanese patients with multiple sclerosis (MS) enrolled in a postmarketing surveillance study of intramuscular interferon beta-1a (IM IFN beta-1a). Methods Safety data were collected from Japanese patients receiving 30 μg weekly IM IFN beta-1a. Pregnancy outcomes and annualized relapse rates (ARR) were analyzed retrospectively in patients who registered into the postmarketing surveillance study. Results A total of 1110 of 1638 patients registered in the postmarketing surveillance study were women. A total of 21 pregnancies (20 patients) resulted in 17 live births, 2 induced abortions, one spontaneous abortion and one unknown outcome. Weights and lengths of the 17 newborns were similar to newborns in the general Japanese population. No complications or malformations were reported. Of these 20 patients, nine experienced relapses in the year after childbirth, two experienced relapses in the year before pregnancy, and one experienced relapses before and during pregnancy. The mean (standard deviation) ARR was 0.94 (2.18) in the year before pregnancy, 0.25 (1.00), 0 (0) and 0 (0) in the three trimesters of pregnancy, and 1.05 (1.81), 0.84 (1.68), 0.63 (2.01) and 0.21 (0.92) in the first four quarters postpartum. Of the five patients who relapsed during the first quarter postpartum, only one had resumed IFN beta-1a treatment for 35 days. Conclusions Although sample size limits our ability to draw definitive conclusions, we did not find evidence that IFN beta-1a has adverse effects on pregnancy outcomes in Japanese patients with MS. Early IFN beta-1a resumption might reduce the risk of relapse within the first quarter postpartum.