Among the total number of newborns, about 11% face hypoxia problems. It is hypoxia that becomes the main cause of premature birth, fetal and newborn mortality, as well as various pathologies. Fetal respiration passes through the placenta with the participation of the erythrocytes. Thus, fetal respiration is affected by the rate of passage of erythrocytes through small blood capillaries. Ultimately, the elasticity, area, and permeability of the erythrocyte membrane have a direct impact on the quality of fetal intrauterine respiration. This article discusses the main methods of studying the dynamic characteristics of erythrocytes and also analyzes the number of anion exchangers on the erythrocyte membrane. The experiment involved 4 pregnant women, two of whom have a risk of premature birth. These patients undergo tocolytic therapy, the purpose of which is to reduce the risk of premature birth. As a result of the study, the dynamics of changes in the ratio of dynamic strength to the elasticity of the erythrocyte membrane, the amount of band 3 protein, as well as the dynamics of the CO2-O2 exchange rate during tocolytic therapy of pregnant patients are determined.