Objective — to establish and characterize the risk factors of maternal deaths (MD) under the conditions of a Russian megalopolis, which emerge in the course of pregnancy, and to justify the possible preventability of maternal mortality (MM). Material and methods. A retrospective multicenter research and analytical study was performed in 27 healthcare facilities of a Russian megalopolis. A total of 648,641 birth histories from 2013 to 2017 were examined. To analyze the main causes of severe pregnancy complications, 3 groups of women were formed: 1) 98 patients with a fatal outcome (a MD group); 2) 792 patients with a near miss event; 3) 27 024 patients with potentially critical (life-threatening) conditions (a stable severe condition with positive changes). An odds ratio was calculated for numerical interpretation of the influence of a certain factor on a specific pregnancy outcome. Results. Out of the total number of births (n=648 641), the proportion of women with a severe pregnancy complication was 4.3%. Out of the total number of severe pregnancy complications, the proportion of MD, near miss events, and potentially life-threatening condition was 0.35, 2.84 and 96.81%, respectively. Twenty-nine main causes of severe pregnancy complications were identified. Severe obstetric and other complications (15.31%), which developed in socially disadvantaged patients (who had no permanent place of residence and were drug addicted, alcoholic, and HIV-infected), as well as intracerebral hemorrhage (12.25%) and severe preeclampsia (10.2%) occupied the first three places among the causes of MD (Group 1). The leading cause of near miss events was obstetric hemorrhage that constituted the largest proportion (40.15%). Uterine rupture (26.52%) and severe preeclampsia (17.17%) ranked second and third, respectively. Severe preeclampsia (PE) (66.03%) and obstetric hemorrhage (32.62%) were the bulk in Group 3 patients with potentially critical conditions. Conclusion. In contrast to global trends, the dominant cause of MD in a Russian megalopolis is severe obstetric complications arising from social deprivation in women. Intracerebral hemorrhage and severe PE are no less significant in the frequency of causes of MD. The development of potentially critical conditions, rather than a near miss event or a fatal outcome, was the greatest chance in severe PE. The current resource of a Russian megalopolis makes it possible to rule out MD caused by venous complications, gastrointestinal diseases (except pancreatic necrosis) and to increase the preventability of MM due to obstetric hemorrhage, severe preeclampsia, uterine rupture, gynecological complications, and eclampsia. The findings allow proposals to update the existing approaches to predicting, preventing, and treating severe pregnancy complications at all stages of medical care for potentially fertile women.