Funding for this research was provided by:
National Natural Science Foundation of China (81602300)
Natural Science Foundation of Jiangsu Province (BK20160139, BK20170699)
the Project on Maternal and Child Health Talents of Jiangsu Province (FRC201791)
Foundation for Natural Science in Higher Education of Anhui Province (KJ2019A0363)
Natural Science Foundation of Jilin Province (81702561)
Received: 29 August 2019
Accepted: 19 June 2020
First Online: 26 June 2020
Ethics approval and consent to participate
: This study was approved by the Ethic Committee of the Obstetrics and Gynecology Hospital Affiliated to Nanjing Medical University and informed consent forms were obtained.
: Not applicable.
: The authors declare that they have no competing interests.