Funding for this research was provided by:
Scientific research projects of health and family planning industry in Hainan Provinc
Received: 5 October 2020
Accepted: 5 November 2020
First Online: 13 November 2020
Ethics approval and consent to participate
: This study was performed following the principles of the Declaration of Helsinki and was conducted according to the National Ethics Guidelines Statement. Informed consent was obtained from all participants.
: Not applicable.
: The authors declare that they have no competing interests.