Funding for this research was provided by:
Natural Science Foundation of Jilin Province (81801465)
Received: 8 February 2020
Accepted: 18 February 2021
First Online: 5 March 2021
: This study was approved by the Medical Ethics Committee of Shenzhen Maternity and Child Healthcare Hospital (SFYLS2019048). Given the retrospective nature of this study, the informed consent waived by the Medical Ethics Committee of Shenzhen Maternity and Child Healthcare Hospital.
: Not applicable.
: We have no conflict of interest to declare.