Funding: the work was supported by the Vklad v buduscheye (Investment in the Future) charity foundation as part of the Stop Coronavirus Together program-campaign.

Author contribution: Ermakova DM, Lomova NA — management of patients participating in the study, article authoring; Dolgushina NV — collection and analysis of literature data, manuscript editing, statistical data analysis; Menzhinskaya IV — execution of the laboratory part of the study, article authoring and editing; Vtorushina VV — execution of the laboratory part of the study

Compliance with ethical standards: the study was approved by the Ethics Committee of Kulakov National Medical Research Center for Obstetrics, Gynecology and Perinatology (Minutes of meeting № 12 of November 26, 2020); all patients signed an informed voluntary consent to participation in the study.