Funding for this research was provided by:
Postdoctoral Science Foundation of Jiangsu Province (2019M652778)
Health and Family Planning Commission of Sichuan Province (C20180289)
Natural Science Foundation of Hainan Province (2020JJ5992)
Received: 17 January 2020
Accepted: 17 August 2020
First Online: 14 September 2020
Ethics approval and consent to participate
: This study and data collection were approved by the Ethics Committee of the Reproductive and Genetic Hospital of CITIC-Xiangya (LL-SC-2019-015). The data were extracted from medical records. Due to the retrospective nature of the study, informed consent was waived.
: Not applicable.
: The authors declare that they have no competing interests.