Abstract： Objective To explore the metabolic phenotype of the adult offspring rats with maternal severe hyperglycemia during pregnancy and overfeeding in early life. Methods The adult Wistar rats were administered intraperitoneally with 20% Streptozotocin (STZ, 50 mg/kg) on day 5 of pregnancy to induce severely gestational diabetes mellitus (SDM) model (blood glucose ≥20 mmol/L). Early postnatal overfeeding models were established through reduction of the number of newborn rats fed by one mother rat. Offsprings were divided into 3 groups according to maternal blood glucose level during the pregnancy and feeding patterns during the lactation period (1) control pups (CP) :maternal euglycemia was achieved during pregnancy and eight pups fed by one mother rat; (2)SDM-normal feeding group: SDM mothers and 8 pups fed by one mother rat;(3)SDM-overfeeding group:SDM mother and 4 pups fed by one mother rat. All pups were fed by standard laboratory chow adlibitum after weaning at 3 weeks of age. The body weight of all pups were measured weekly after weaning. At the age of 26 weeks, the systolic blood pressure (SBP), diastolic blood pressure (DBP) ,heart rate (HR) and metabolic markers, including fasting plasma glucose (FPG), fasting insulin (FINS), total triglyceride (TG), total cholesterol (TC), low density lipoprotein-cholestrol (LDL-C)and high density lipoprotein-cholestrol (HDL-C) were measured in all 3 groups. ANOVA and LSD test were applied in statistical analysis. Results The average plasma glucose level was significantly higher in the SDM mothers than in the controls [(28.34±5.14) mmol/L va (6.25±1.41) mmol/L,P＜0.05]. After weaning at 3 weeks, the weight of SDM-overfeeding group and SDM-normal feeding group was lighter than that of CP group [(43.63±4.83) g, (31.45±10.21) g vs (55.75±8.41) g,P＜0. 05], meanwhile, that of the SDM-overfeeding group were heavier than that of the SDM-normal feeding group (P＜0. 05). Pups in SDM-overfeeding group exhibited catch-up growth during the lactation period, and those in SDM-normal group showed catch-up growth at both lactation period and childhood. At 26 weeks of age, the systolic blood pressure and TG level of pups in SDM-normal feeding and overfeeding group were (153.31 ± 13.91) mm Hg and (147.21 ± 12.29) mm Hg, and (0. 73±0. 22) mmol/L and (0. 71±0.49) mmol/L, respectively, which were higher than those of the CP group [( 132.21 ± 11.26) mm Hg, and (0. 37 ± 0. 08) mmol/L, P＜0.05], but no significant difference was found between the two SDM groups (P＞0.05). There was no difference in FPG levels among the three groups, but the FINS level and HOMA-IR in the SDM-overfeeding group were higher than in the SDM normal feeding and CP group [( 12. 552 ± 3.260) mU/L vs (9.067 ± 1.782) mU/L and (8.590± 0.806) mU/L, 2.400± 0.624 vs 1.797 ± 0.508 and 1.729 ± 0.246; P＜0.05].Conclusions Fetal exposure to maternal severe hyperglycemia during pregnancy may lead to low birth weight infant who will exhibit postnatal catch-up growth. This may lead to the increased risk of metabolic syndrome in the offspings when they grow up, and this process would be accelerated by early overfeeding.