Received: 26 November 2020
Accepted: 18 August 2021
First Online: 5 October 2021
: Ethical approval was obtained from the hospital Institutional Review Board (Shanghai First Maternity and Infant Hospital No. KS20106). All methods were performed in accordance with the guidelines of the Declaration of Helsinki. Furthermore informed consent was obtained from every participant. Participants were assured that the information collected in this study was confidential and anonymous, and their participation was totally voluntary.
: Not applicable.
: The authors declare that they have no competing interest.