1. Department of Obstetrics and Gynecology, Third Affiliated Hospital of Soochow University, Changzhou, China;
2. Department of Obstetrics and Gynecology, The First People's Hospital of Changzhou, Changzhou, China;
3. Department of Obstetrics and Gynecology, Hangzhou Maternity and Child Health Care Hospital, Hangzhou, China;
4. Department of Obstetrics and Gynecology, Hangzhou Women's Hospital, Hangzhou, China