Funding for this research was provided by:
the National Natural Science Foundation of China (81670635)
the Youth Fund under the Fujian Provincial Health and Family Planning Commission (2017-1-97)
Article History
Received: 27 June 2019
Accepted: 27 August 2019
First Online: 18 September 2019
Ethics approval and consent to participate
: Not applicable.
: Not applicable.
: The authors declare that they have no competing interests.