Tasks of investigation were concluded the characterization of insulin resistence (IR) and hormonal features in patients with prediabetes and influence of diet or metformin on the course of pregnancy and perinatal complications. There were examined 61 womans. The OGTT, definition of insulin levels in plasma and index IR were performed in all patiens. OGTT and index IR were normal in 14 womans (control group I). OGTT was normal but index IR was impared in 33 womans (group IR - II). From this group 22 womans were treated with diet (II A group) and 11 womans treated with metformin (IIB group). OGTT and index IR were abnormal in 14 womans (impared OGTT - III group), they were treated with metformin. Dose of metformin was 1500 mg/d, threatment was continueted for 3-4 manths. Conclusion: Used indexes IR basal and two hour after glucose load were significant in definition of normal and decreased insulin sensitivity (IR). Presence of IR is accompanied by high level of free testosterone in blood without impared secretion of ovarian and suprarenal androgens. There was impared sensitivity of endometrium of secretory stage. The frequency of obstetric and perinatal complications in patients receiving diet not differ from patients treated with metformin. There was only a tendercy to low frequency of threatening miscarriages befor 12 weeks of gestations in paitiens receiving metformin. Development of GDM was observed in 13,1 % of patiens only with presence of IR. The use of metformin in pregravidal stage preserved the development of macrosomia in offsprings of patients with prediabetes.