Funding for this research was provided by:
National Natural Science Foundation of China (31571508)
Chongqing Health and Family Planning Commission (2015MSXM047)
Text and Data Mining valid from 2018-06-07
Received: 19 September 2017
Accepted: 23 May 2018
First Online: 7 June 2018
Ethics approval and consent to participate
: A written informed consent was obtained from each participant. Approval for the study was obtained from the institutional ethical committee of Chongqing medical university (CQMU2015016).
: The authors declare that they have no competing interests.
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