Funding for this research was provided by:
Health and Family Planning Commission of Chengdu (2015009)
Received: 23 August 2019
Accepted: 5 November 2019
First Online: 13 November 2019
Ethics approval and consent to participate
: We obtained ethical approval for this study from the Medical and Health Research Ethics Committee in Second people’s Hospital of Chengdu, the Second Affiliated Hospital of Chengdu College, Nuclear Industry 416 Hospital of Chengdu, and Chongqing Medical University. All patients gave an informed consent to study participation. All the pertinent guidelines required by our institution for the preparation of retrospective studies have been followed.
: Not applicable.
: The authors declare that they have no competing interests.