1. Department of Preventive Medicine, Korea University College of Medicine, Seoul, Korea.
2. Department of Obstetrics and Gynecology, Kyung Hee University Hospital at Gangdong, Kyung Hee University College of Medicine, Seoul, Korea.
3. Department of Obstetrics and Gynecology, College of Medicine,The Catholic University of Korea, Seoul, Korea.
4. Department of Obstetrics and Gynecology, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea.
5. Department of Obstetrics and Gynecology, MizMedi Hospital, Seoul, Korea.
6. Department of Obstetrics and Gynecology, CHA Bundang Medical Center, CHA University School of Medicine, Seongnam, Korea.
7. Department of Obstetrics and Gynecology, Gangnam Severance Hospital, Institute of Women's Life Medical Science, Yonsei University College of Medicine, Seoul, Korea.
8. Department of Obstetrics and Gynecology, Research Institute of Medical Science, Konkuk University Medical Center, Konkuk University School of Medicine, Seoul, Korea.
9. Department of Obstetrics and Gynecology, Kangwon National University Hospital, School of Medicine Kangwon National University, Chuncheon, Korea.
10. Mirae & Heemang Obstetrics and Gynecology Clinic, Seoul, Korea.
11. Dr Kim's OB-GYN Clinic, Daegu, Korea.