Discontinuation of disease-modifying treatments in multiple sclerosis to plan a pregnancy: A retrospective registry study

Background: For safety reasons multiple sclerosis (MS) treatment guidelines recommend stopping or delaying the onset of disease-modifying therapies (DMT) before a planned pregnancy, but disease stability after DMT discontinuation is not well studied. The objective of this study is to describe the course of MS in patients who interrupted DMT before a planned pregnancy. Methods: This was a retrospective study using 2008-2016 data from a multicenter register of pregnancies in women with MS. In this paper, we present data from the subgroup of women with relapsing-remitting MS (RRMS) who interrupted DMT to try to conceive. Data from 1 and 3 years before DMT interruption, the period between DMT interruption and conception or resuming DMT, during pregnancy and one year postpartum were analyzed. Annualized relapse rates (ARR), Expanded Disability Status Scale (EDSS) scores, and magnetic resonance imaging (MRI), obstetric, and neonatal data were collected. Results: Twenty-seven women interrupted DMT (19 beta-interferon, 5 glatiramer acetate, 2 natalizumab and 1 fingolimod) to try to conceive. After a mean of 10.6 months 6 women stopped trying to conceive and resumed DMT, while 21 women became pregnant after a mean of 7.0 months. In the overall cohort, in the period from when DMT was discontinued to when pregnancy was confirmed or DMT resumed, the ARR was 1.08, which was significantly higher than the ARR 1 year (0.44; p = 0.01) and 3 years (0.4; p = 0.06) before DMT discontinuation. The mean EDSS score when pregnancy was confirmed or DMT resumed was significantly higher than at DMT discontinuation (1.8 vs 1.36, p = 0.011). In the subgroup of patients who became pregnant, the ARR in the untreated period before pregnancy was 0.98, which was significantly higher than the ARR 1 year (0.38; p = 0.03) and 3 years (0.39; p = 0.0077) before DMT discontinuation. The ARR decreased to 0.51 during pregnancy and then increased to 0.76 during the first postpartum trimester (not significant). One year after delivery, the mean EDSS score (1.86) was significantly higher than at DMT cessation (1.35, p = 0.027) or pregnancy confirmation (1.45, p = 0.026). Patients who suffered relapses following DMT cessation before becoming pregnant had an 11-fold higher risk of relapse during pregnancy (relative risk [RR] = 11.1 [95%CI 1.6, 75], p = 0.002) and a 3-fold higher risk during the postpartum year (RR = 3.0 [95%CI 1.3,6.6], p = 0.007) than those who did not suffer relapses in period between DMT withdrawal and pregnancy. Conclusions: In this retrospective registry study, discontinuation of DMT (mostly immunomodulatory drugs), to try to conceive resulted in an increase in MS relapse rates and disability progression.