Funding for this research was provided by:
Chongqing Science and Technology Commission (cstc2016shmszx130048)
the Health and Family Planning Commission of Chongqing grants (2016ZDXM017)
Article History
First Online: 23 January 2019
Compliance with Ethical Standards
:
: This study was supported by the Health and Family Planning Commission of Chongqing grants (2016ZDXM017), Chongqing Science and Technology Commission grants (cstc2016shmszx130048).
: Huan-huan JI, Xue-wen TANG, Zhi DONG, Lin SONG, and Yun-tao JIA declare that they have no conflict of interests.