RT Journal Article SR Electronic T1 004 Pregnancy-related relapse in natalizumab, fingolimod and dimethyl fumarate-treated women with multiple sclerosis JF BMJ Neurology Open JO BMJ Neurol Open FD BMJ Publishing Group Ltd SP A2 OP A2 DO 10.1136/bmjno-2021-ANZAN.4 VO 3 IS Suppl 1 A1 Yeh, Wei Z A1 Widyastuti, Putu A A1 Walt, Anneke Van der A1 Stankovich, Jim A1 Havrdova, Eva K A1 Horakova, Dana A1 Vodehnalova, Karolina A1 Ozakbas, Serkan A1 Eichau, Sara A1 Duquette, Pierre A1 Kalincik, Tomas A1 Patti, Francesco A1 Boz, Cavit A1 Terzi, Murat A1 Yamout, Bassem A1 Lechner-Scott, Jeannette A1 Sola, Patrizia A1 Skibina, Olga A1 Barnett, Michael A1 Onofrj, Marco A1 Sá, Maria J A1 McCombe, Pamela A1 Grammond, Pierre A1 Ampapa, Radek A1 Grand’Maison, Francois A1 Bergamaschi, Roberto A1 Spitaleri, Daniele LA A1 Pesch, Vincent Van A1 Cartechini, Elisabetta A1 Hodgkinson, Suzanne A1 Soysal, Aysun A1 Saiz, Albert A1 Gresle, Melissa A1 Uher, Tomas A1 Maimone, Davide A1 Turkoglu, Recai A1 Hupperts, Raymond MM A1 Amato, Maria Pia A1 Granella, Franco A1 Oreja-Guevara, Celia A1 Altintas, Ayse A1 Macdonell, Richard A1 Castillo-Trivino, Tamara A1 Butzkueven, Helmut A1 Alroughani, Raed A1 Jokubaitis, Vilija G A1 Registry, MSBase YR 2021 UL http://neurologyopen.bmj.com/content/3/Suppl_1/A2.1.abstract AB Objective To investigate pregnancy-related disease activity in a contemporary multiple sclerosis (MS) cohort.Methods Data were obtained from the MSBase Registry. Term/preterm pregnancies conceived from 2011-2019 were included (modern cohort). Annualised relapse rates (ARR) were calculated before, during and after pregnancy. Predictors of intrapartum and early postpartum (1st3 months) relapse were determined by clustered logistic and Cox regression analyses, respectively.Results We included 1640 pregnancies from 1452 women. Disease-modifying therapy (DMT) used in the one-year preconception included natalizumab (n=219), fingolimod (n=147), dimethyl fumarate (DMF; n=57) and low-efficacy therapies (n=845). Preconception ARR by DMT class used before conception were: natalizumab, 0.29 (95% CI 0.22-0.37); fingolimod, 0.37 (0.28-0.49); DMF, 0.24 (0.13-0.41); low-efficacy, 0.29 (0.25-0.33); and none, 0.24 (0.19-0.31). Among women who used fingolimod or natalizumab, ARR increased during pregnancy. Intrapartum ARR decreased in preconception DMF, low-efficacy or no DMT groups. ARR spiked after delivery across all DMT groups. Natalizumab continuation into pregnancy reduced the odds of relapse during pregnancy (OR 0.76 per month [0.60-0.95], p=0.017). DMT re-initiation with natalizumab protected against postpartum relapse (HR 0.11 [0.04-0.32], p<0.0001). Breastfeeding women were less likely to relapse (HR 0.61 [0.41-0.91], p=0.016).Conclusion Women with MS prescribed natalizumab or fingolimod preconception had higher rates of intrapartum and postpartum relapse. In women considered to be at high relapse risk, use of natalizumab before pregnancy and continued up to 32-34 weeks gestation, with early re-initiation after delivery is an effective option to minimise relapse risks. Strategies of DMT use have to be balanced against potential foetal/neonatal complications.