Funding for this research was provided by:
Hubei Provincial Population and Family Planning Commission (WZ17Z08)
Article History
Received: 29 June 2019
Accepted: 31 January 2020
First Online: 21 February 2020
Ethics approval and consent to participate
: Not applicable.
: All authors reviewed and consented to the publication of the manuscript.
: All authors declare no conflict of interest.