Natalizumab Washout Prior to Pregnancy Associated with Increased Relapses

Natalizumab is often used for severe multiple sclerosis (MS). Because this treatment blocks lymphocyte entry into the central nervous system (CNS), its withdrawal (e.g., before attempting pregnancy) has been associated with return of disease activity. Investigators used a multicenter registry to track 74 pregnancies in 70 women with relapsing-remitting MS taking natalizumab and compared relapses with those in 350 pregnancies in 345 women (control patients) who were either untreated or taking injectable MS therapies.

For control patients, the relapse profile was consistent with prior studies: stable prior to conception, reduced during pregnancy, and increased after delivery. For those on natalizumab, relapse rate was stable prior to conceptio…