The total serum N-glycome (TSNG) comprises the N-glycans from all serum proteins, which are to a large extent liver- (acute-phase proteins) and plasma cell-derived (antibodies) (15, 26). Interestingly, the TSNG has been shown, in a small sample set, to differ between healthy individuals and those with RA, and undergoes clear alteration throughout pregnancy and the following postpartum period (27, 28). However, it is hitherto unknown which TSNG characteristics are associated with the disease activity of RA, and changes thereof throughout pregnancy. Recent developments in mass spectrometry (MS)-based high-throughput glycosylation analysis have provided the opportunity to acquire information on TSNG N-glycan complexity, antennarity, galactosylation, fucosylation, as well as on the presence and linkage of sialic acids (α2,6- vs. α2,3-linkage) (29, 30). The latter appears to be of high immunological relevance, since the α2,3-linked sialic acids are required for sialyl-Lewis X formation implicated in the interaction with selectins (29, 30).