The aim of our work was to evaluate changes in levels of oxidised low-density lipoprotein (Ox-LDL) during pregnancy and how they correlate with changes in LDL size and serum total antioxidant status (TAS). LDL peak and mean particle diameter (LDL-PPD and LDL-MPD, respectively) and the relative proportion of 3 LDL subfractions were quantified. We evaluated plasma levels of Ox-LDL and serum levels of TAS, total cholesterol (Chol), triglycerides (TG), apolipoprotein A-I (apo A-I), apolipoprotein B (apo B), HDL-cholesterol (HDLc) and LDL-cholesterol (LDLc). A longitudinal study was performed in the three trimesters (T1-T3) of pregnancy in normal pregnant women (n = 23) and a non-pregnant group (n = 18) was used as control. TG levels were significantly elevated whereas LDL-MPD and LDL-PPD were significantly reduced in T1 compared to controls. Ox-LDL, TG, Chol, apo B and LDLc rose markedly throughout pregnancy with significant changes between each trimester; LDL-PPD, LDL-MPD and TAS levels decreased significantly from T1 to T3. Changes in LDL size and in Ox-LDL and TAS levels were more pronounced between T1 and T2 than between T2 and T3. HDLc and apo A-I reached peak concentration in T2 but decreased in T3. TG concentrations correlated inversely with LDL size and positively with Ox-LDL; Ox-LDL was positively and strongly correlated with LDLc. Moreover, relative changes in the levels of Ox-LDL correlated inversely with relative changes in LDL size and TAS between trimesters. In conclusion, during human gestation the change in LDL profile towards smaller species and the decrease in serum TAS are closely associated with increased levels of Ox-LDL. The exact physiological role of the increments in Ox-LDL during pregnancy remains to be clarified.