1. Department of Obstetrics and Gynecology, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
2. Department of Obstetrics and Gynecology, Shanghai Jiaotong University Affiliated International Peace Maternity & Child Health Hospital of the China Welfare Institute, Shanghai, China
3. Department of Obstetrics and Gynecology, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, Shanghai, China