Funding for this research was provided by:
Health and Family Planning Commission Project of Shaanxi Province (NO. 2016D063)
China Medical Board foundation (NO. 06-841)
Received: 3 August 2019
Accepted: 26 June 2020
First Online: 29 July 2020
Ethics approval and consent to participate
: The retrospective study was approved by the Ethics Committee of the First Affiliated Hospital of Xi’an Jiaotong University (Grant No. XJTU1AF2015LSL-073), and the team was approved to access the data, and the clinical research project (NO. XJTU1AF-CRS-2015-003) has been established.
: Not applicable.
: The authors declare that they have no competing interests.