Funding for this research was provided by:
Beijing Municipal Science and Technology Commission (D151100001915001)
Beijing Municipal Administration of Hospital’s Youth Programme (QML20151302)
The Capital Health Development Research Fund (2018-4-2113)
Beijing Obstetrics and Gynecology Hospital, Capital Medical University (fcyy201601)
Special Program for Development of Clinical Medicine of Beijing Municipal Administration of Hospitals (ZYLX201705)
Article History
Received: 8 May 2018
Accepted: 1 November 2018
First Online: 8 November 2018
Compliance with ethical standards
:
: The authors declare that they have no conflict of interest.
: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. This retrospective study was approved by the Ethic Committee (EC) from the Beijing Obstetrics and Gynecology Hospital.
: Informed consent was obtained from all individual participants included in the study.