The study of the issue of the etiopathogenesis of anembryonic pregnancy is of great importance. The aim — of this study is to investigate the state of endotoxemia and anti-endotoxin immunity in patients with anembryonic pregnancies in the first trimester (up to 12 weeks of pregnancy). Material and methods. A retrospective analysis of endotoxin concentrations and anti-endotoxin immunity was carried out in 98 patients admitted to the gynecological department with a diagnosis of anembryonic pregnancy and with a gestational period of 5 to 12 weeks (the main group). The control group included 30 patients with progressing pregnancies of similar duration. The average age of the patients in both groups was 25.3±3.01 years. Clinical and laboratory examination of the patients was carried out using standard and specialized (bacteriological, bacterioscopic, histological, polymerase chain reaction) methods. To determine the level of endotoxin in the blood, the LAL test was used to assess the state of anti-endotoxin immunity — a method of screening and evaluating a patient’s immune status by means of immunoenzyme analysis. Results. In a histological study, 88.8% of patients with anembryonic pregnancy showed signs of long-term current chronic endometritis in the acute stage, and 11.2% showed signs of acute endometritis; persistent urogenital infections were found in the uterine cavity of patients with chronic endometritis, while patients with acute endometritis were found to have viral-bacterial infections. It is shown that chronic inflammation plays a primary role in the pathogenesis of anembryonic pregnancies, which is confirmed by the increased level of endotoxin in the blood of patients and the state of the humoral part of anti-endotoxin immunity. Conclusion. For patients with anembryonic pregnancies and a history of chronic endometritis, the results of the study attest to the need for etiotropic treatment after involution, including antibacterial therapy and the correction of anti-endotoxin immunity.