Plasma lipoproteins were studied longitudinally at the 1st, 2nd, and 3rd trimester of gestation and at postpartum and postlactation in 12 age-matched PGDM women, 9 GDM women, and 12 healthy control subjects. FPG and HbA1c were higher in every case in PGDM women than in control subjects, whereas in GDM patients, glucose was augmented only after parturition. FFA and beta-hydroxybutyrate levels were higher in both PGDM and GDM patients than in control subjects during gestation but not after parturition. Total TGs and VLDL, LDL, and HDL TGs increased with gestational time in the three groups and declined at postpartum, and although total cholesterol and VLDL, LDL, and HDL cholesterol followed a similar trend, their rise was less pronounced, and the decline after parturition was slower than that of the TGs in the three groups, with no difference among them. The VLDL TG/cholesterol ratio declined in the three groups at the 3rd gestational trimester, whereas in both LDL and HDL, the TG/cholesterol ratio, but not the cholesterol/phospholipid ratio, increased during gestation in the three groups, indicating a specific enrichment of TGs in these particles. The increase in apoA-I and apoB with gestation was parallel to the respective changes in HDL and LDL cholesterol and, again, no difference was observed between the three groups. Plasma levels of beta-estradiol, progesterone, and prolactin increased sharply with gestation and declined at postpartum in the three groups, but absolute values of beta-estradiol and prolactin, at the three trimesters of gestation, were lower in PGDM patients, but progesterone levels were lower than controls in GDM women only at the 3rd trimester. (ABSTRACT TRUNCATED AT 250 WORDS)