Funding for this research was provided by:
National Key R&D Program of China (2017YFC0909900)
Hubei Province health and family planning scientific research project (WJ2017M118)
Text and Data Mining valid from 2019-01-28
Received: 13 September 2018
Accepted: 19 December 2018
First Online: 28 January 2019
Compliance with ethical standards
: All authors have no conflict of interest to disclose.
: 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.
: Informed consent was obtained from all individual participants included in the study.