Funding for this research was provided by:
Guangxi Medical and Health Self-funding Project (No Z2014379, No Z20180022)
Liuzhou Science and Technology Bureau Project (No 2014J030422, 2018BJ10504, 2018BJ10502)
Text and Data Mining valid from 2019-11-11
Received: 4 August 2019
Accepted: 12 September 2019
First Online: 11 November 2019
Ethics approval and consent to participate
: This study was approved by the Institutional Review Board of Liuzhou Maternity and Child Healthcare Hospital.
: Not applicable.
: The authors declare that they have no competing interests.