Aim. To elucidate the character of the relationship between gestational body weight gain (GBWG) and carbohydrate/lipid metabolism during pregnancy. Material and methods. This prospective cohort study enrolled 85 women with full-term sigleton pregnancy in the absence of signs of diabetes mellitus or severe somatic pathology including 15 ones with subnormal GBWG, 35 with excessive GBWG, and 36 with recommended GBWG. Detection of gestational body weight gain, carbohydrate tolerance test, measurement of baseline and stimulated insulin secreation, lipidograms obtained in the first, second, and third trimesters. Results. The biochemical profile in the patients with pathological GBWG has the following peculiarities in comparison with that of the women with recommended GBWG during pregnancy. The women with excessive GBWG in the second and third trimesters are characterized by enhanced levels of baseline and stimulated insulin secretion, high HOMO-IR index and LDLP concentration (p<0.05). The women with subnormal GBWG in the first trimester have a higher fasting blood glucose level whereas in the third trimester both fasting glycemia and insulin concentration in response to standard carbohydrate loading decrease to below the respective normal values (p<0.05). The biochemical and hormonal characteristics of carbohydrate and lipid metabolism undergo secondary changes following body mass variations. Conclusion. The results of this study show that changes in sensitivity to insulin are in all probability the consequence of pathological enhancement of body mass rather than its cause.