High incidence of missed abortion induces to search for its causes. Apart from genetic and anatomic uterine factors, the state of the decidual endometrium and implantation zone of chorionic structures of the gestational sac are of particular interest. Direct visualization of the intact decidual endometrium is possible with embryoscopy, however, there is lack of presented data of normal and pathological signs of the endometrium during pregnancy. This paper describes the changes of the endometrium in missed abortion obtained by hysteroscopy in 160 women with nonprogressive pregnancy after ART protocols. High incidence of vascular disorders is determined, namely perivascular hemorrhage (70%), thrombosis of small-caliber endometrial vessels (36.9%), necrosis of the decidual endometrium and areas of the endometrium ejection beyond the implantation zone as a source of vaginal bleeding (10%). In addition, a high incidence of capsular decidual membrane defects are detected, namely, dystrophy, thinning and necrosis (60.6%).