The aim of the study was to analyze the activity of erythrocyte acetylcholinesterase in puerperia with a complicated and physiological course of puerperia. A survey of 41 puerperas (mean age 26.5±2.1) who were hospitalized in the physiological department of the 3rd City Clinical Hospital named after E.V. Klumova, Minsk. All patients were divided into the following groups: 1st - 19 puerperas with a physiological course of labor and the postpartum period (mean age 25.2±2.3); 2nd - 22 puerperas with impaired contractile function of the uterus during childbirth and the postpartum period (mean age 27.0±2.2). The study of AChE activity in erythrocytes was carried out by the kinetic method using Cormay test kits (Poland) on an FP-900 biochemical analyzer (Finland). The results of the study allow us to consider the activity of acetylcholinesterase in erythrocytes, the echographic size of the uterine cavity according to sonography, and the level of uterine tone according to the hysterogram as significant markers of impaired labor contractile activity of the myometrium after childbirth. The threshold value of the size of the uterine cavity, the upward deviation from which indicates the formation of postpartum subinvolution of the uterus, was 15.3 mm at AUC 0.99±0.02 (p < 0.001; HR 90.2%, DS 88.4%). The threshold value of the uterine tone, the downward deviation from which indicates a violation of the contractile function of the uterus in the puerperal, was 4.7 mm Hg. Art. at AUC 0.9±0.015 (p < 0.001; HR 96.3%, DS 88.5%). The threshold point of AChE activity was 11745.4 U/l with an AUC ROC curve of 0.82±0.07 (p < 0.001; PN 94.2%, DS 61.1%), which allows us to regard the studied parameter as a classifier physiological course of the postpartum period and postpartum subinvolution of the uterus. When choosing means of influencing postpartum subinvolution of the uterus, preference should be given to drugs and physiotherapeutic methods that have a stimulating effect on the contractile function of the uterus in order to eliminate the pathologically enlarged cavity and prevent the development of hemorrhagic and inflammatory complications.