Funding for this research was provided by:
Natural Science Foundation of China (81571412)
Beijing Municipal Administration of Hospitals Clinical Medicine Development of Special Funding Support (ZYLX201406)
Beijing Obstetrics and Gynecology Hospital (FCYY201920)
Received: 11 May 2020
Accepted: 26 December 2020
First Online: 2 February 2021
Ethics approval and consent to participate
: The study was approved by the local research and ethics committee of the Beijing Obstetrics and Gynecology Hospital (No. 2016-KY-012). All patients included in this study signed an informed consent form.
: All authors consented to publication.
: The authors report no conflicts of interest.