Disease modifying therapies and disease activity during pregnancy and postpartum in a contemporary cohort of relapsing Multiple Sclerosis patients.

Background: In Multiple Sclerosis (MS) women, therapeutic management for pregnancy planning and during pregnancy still represents a challenge regarding timing of disease-modifying therapies (DMT) stop, risk of disease reactivation and potential fetal toxicity. The objective of this study was to describe disease activity during pregnancy and postpartum depending on treatment status before conception in women with MS.

Methods: 339 MS patients who have achieved a pregnancy between 2007 and 2017 were included. Women were classified according to their exposure to DMT in the 18 months period prior to pregnancy (untreated / first- / second/third-line treatment).

Results: 122 women were not exposed to DMT prior to conception, whereas 147 were exposed to first-line DMT and 70 to second/third line DMT (73% to natalizumab and 23% to fingolimod) before conception. In the first-line group, the ARR decreased from 0.39 during the year before conception to 0.21 during pregnancy, whereas it increased in the second/third-line group from 0.59 to 0.78. 47.1% of the second/third-line group faced at least one relapse during pregnancy and the time from conception to first relapse was significantly shorter in this group (p < 10). The risk of relapse during pregnancy and postpartum was associated with occurrence of pre-conception relapses and second/third line DMT exposure before pregnancy.

Conclusion: Careful consideration should be given to natalizumab and fingolimod exposed patients before conception as they are at higher risk of reactivation of MS during pregnancy.