Funding for this research was provided by:
Natural Science Foundation of Zhejiang Province (GF20F020063)
Received: 8 May 2020
Accepted: 6 January 2021
First Online: 25 January 2021
Ethics approval and consent to participate
: This study is observational and presents no more than minimal risk of harm to subjects and involves no procedures for which written consent is normally required outside the research context. Hangzhou Women Hospital Research Ethics Board approved the waiver of informed consents (NO. 2017-001) for this study according to section 39 of Measures for the Ethical Review of Biomedical Research Involving Humans published by National Health Commission of the People’s Republic of China (CLI.4.282697).
: Not applicable.
: The authors declare that they have no competing interests.