Objective. To study the fractions of histone proteins and enzymes of energy metabolism of succinate dehydrogenase (SDH) and α- glycerophosphate dehydrogenase (α-GPDH) in peripheral blood lymphocytes at the physiological and not developing pregnancy. Material and methods. Three groups of patients were examined. The main group (I) included 30 women with physiological pregnancy, the II main group consisted of women with not developing pregnancy (30 people), the control group (III) - 20 healthy non-pregnant women. Results. The study revealed a significant increase in the content of histone proteins at physiological development of pregnancy, especially fractions H2A, H3, H4 and H2B as well as compared with the control. In patients of group II, the content of the total fraction H2A, H3, H4 histone remained almost at the level of non-pregnant women and significantly differed from those of the first group. The activity of the mitochondrial enzyme - SDH and α-GPDH declined in the main group I, group II patients have a significant decrease in activity compared to non-pregnant women received only α-GPDH. Conclusion. The identified changes are likely needed to reduce the activity of lymphocytes and the development of tolerance to the tissues of the fetus. Changes are less pronounced in women with non-developing pregnancy, some indicators do not differ from the control group.