Objective: to investigate the characteristics of cytotrophoblast invasion in complete placenta previa and increta. Material and methods. Three groups of placentas and amputated uteri were examined. These were: 1) 10 placentas at 20—22 weeks’ gestation after drug-induced abortion; 2) 4 uteri with typical placentation at 34—36 weeks and wall ruptures; 3) 12 uteri with ultrasound-confirmed complete placenta previa and subsequent hysterectomy (at 34—36 weeks.) due to massive bleeding. In all cases, the sections were stained with hematoxylin and eosin, azan by the Mallory’s method; immunovisualization of invasive cells with the marker cytokeratin 8 was also used. In Groups 2 and 3, the uterine distribution density of invasive cells was compared in a standard slice area (×200) separately, within the endometrium and myometrium. Results. Complete placenta previa was found to have the following characteristics: 1) all the uteri exhibited focal or diffuse friable, or thick scars after cesarean section; 2) multiple active anchor villi with villous cytotrophoblast layers, which were characteristic of Group 1 placentas and absent in the uteri women of Group 2; 3) bays diagnosed in the basal endometrium with ingrown villi (placenta increta); 4) a morphometrically significant increase in the distribution density of interstitial cytotrophoblast in the endometrium and only a similar trend in the myometrium. Invasive cells did not penetrate into the area of scars. Failure of the second wave of cytotrophoblast invasion was confirmed by incomplete gestational restructuring and partial obliteration of the myometrial radial arteries. Conclusion. Real risks for severe clinical forms of abnormal placentation declare more stringent indications for surgical delivery