Funding: the study was supported by the “Investment to the Future” Sberbank Charitable Foundation within the framework of “Stop the Coronavirus Together” initiative.

Author contributions: Dovgan AA, Drapkina YuS — patient management, manuscript writing; Dolgushina NV — literature research, manuscript editing, statistical analysis; Menzhinskaya IV, Krechetova LV — laboratory research, manuscript editing; Sukhikh GT — conclusive editing and approval of the manuscript.

Compliance with ethical standards: the study was approved by Ethical Review Board at Kulakov National Medical Research Center for Obstetrics, Gynecology and Perinatology (Protocol No. 12 of November 26, 2020). All participants provided informed consent for the study.