1. Department of Obstetrics and Gynecology, Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing, China (mainland)
2. Department of Obstetrics and Gynecology, Beijing Shijitan Hospital, Capital Medical University, Beijing, China (mainland)
3. Department of Obstetrics and Gynecology, The Second Hospital of Jilin University, Changchun, Jilin, China (mainland)