Funding for this research was provided by:
National Natural Scientific Foundation of China (81378174)
Shanghai Municipal Commission of Health and Family Planning (20154Y0055)
Yuhang District Key Scientific Research Project for Medical Sciences (2015008)
Received: 17 September 2017
Accepted: 11 January 2018
First Online: 23 January 2018
Ethics approval and consent to participate
: This research has been approved before it began by the ethics committee of the Obstetrics and Gynecology Hospital of Fudan University. All the patients included in this research had signed informed consent, and no bad effect occurred during this process.
: The authors declare that they have no competing interests.
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