Apolipoprotein M (apoM) is mainly associated with high-density lipoprotein in human plasma. Despite several studies suggesting apoM as an anti-atherogenic, its function is not yet fully understood. Plasma apoM was measured in normal pregnancies at four different gestational ages and in the postpartum period to investigate whether the concentration of apoM changes during pregnancy. In addition, apoM was measured at 13 weeks in women who subsequently developed preeclampsia, gestational diabetes, recurrent miscarriage, or small-for-gestational age babies, and in women with uncomplicated pregnancies. The plasma concentrations of apoM increased during pregnancy to reach highest levels in the postpartum period. Thus, plasma apoM in non-pregnant women was around 0.77 micromol/l, 0.88 micromol/l at 40 gestational weeks, and 1.05 micromol/l in the postpartum period (p < 0.0001). No differences in plasma concentrations of apoM were found among the studied pregnancy complications.