Risk of relapses during pregnancy among multiple sclerosis patients

Background: Relapse rate in women with Multiple Sclerosis (MS) is reduced during pregnancy especially in the third trimester according to the previous studies. Objectives: To measure the annual relapse rate (ARR) in women with MS during pregnancy. Methods: A retrospective study was conducted using prospectively collected data from two MS registries in Kuwait and Lebanon. Demographics, clinical characteristics including relapses, disease modifying therapies (DMTs) and their washout periods were extracted. The annual relapse rates pre and post pregnancies were compared and the relationship between relapses and prior use of different DMTs was assessed. Results: Data of 164 pregnancies (132 MS patients) was reviewed. Mean age and disease duration at the time of pregnancy confirmation were 32.4 ± 5.3 and 7.8 ± 4.7 years respectively. Most patients (91.7%; n = 121) were on DMTs in the year prior to pregnancy. The pre-pregnancy ARR was 0.10 (95% CI: 0.04 – 0.13), which increased to 0.20 (95% CI: 0.13– 0.29) during pregnancy. Most relapses occurred either during the 1st (ARR = 0.24; 95% CI: 0.12 – 0.44) or 3rd (ARR = 0.32; 95%CI: 0.17 – 0.53) trimesters. Fingolimod (31.8%) and natalizumab (22.7%) were the most commonly prescribed DMTs in patients who sustained relapses during pregnancy. The mean washout period was significantly longer among subjects with relapses (9.3 ± 6.6 vs. 2.5 ± 3.9; p < 0.001) than those of without relapses. Conclusions: Relapse rate during pregnancy was higher than previous studies conducted in patients on platform therapies or untreated. Longer washout period prior to conception was associated with increased relapses especially in fingolimod and natalizumab treated patients.