Funding for this research was provided by:
Shandong Provincial Natural Science Foundation, China (ZR2016HB37)
Shandong Medical Science and Technology Development Plan Project (2017WSA01044, 2017WS433)
Science and technology projects of Jinan health and family planning commission (2016-1-50)
Text and Data Mining valid from 2019-08-19
Received: 5 May 2019
Accepted: 24 July 2019
First Online: 19 August 2019
Ethics approval and consent to participate
: The protocol of this study was approved by the local Ethical Committee of the Qilu Hospital of Shandong University (KYLL-2017(KS)-088). All volunteers received information concerning their participation in the study and gave written informed consent.
: Not applicable.
: The authors declare that they have no competing interests.