Kleerekooper I, et al. - This study was conducted to examine multiple sclerosis (MS) disease activity and disability progression in pregnancy-related natalizumab (NTZ) discontinuations in relation to time to conception and NTZ concentrations. Following NTZ discontinuation, early conception was correlated with a reduced risk of disease activity and disability progression. In patients with previously active MS, a continuation of NTZ treatment until confirmed pregnancy ought to be considered. However, the advantages of continuing the drug until pregnancy had to be balanced against the uncertainties in postnatal outcomes.