1. Department of Obstetrics and Gynecology, Severance Hospital, Yonsei University College of Medicine, Seoul, South Korea
2. Institute of Women’s Life Medical Science, Yonsei University College of Medicine, Seoul, South Korea
3. Department of Obstetrics and Gynecology, Uijeongbu St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, South Korea
4. Department of Obstetrics and Gynecology, College of Medicine, Korea University, Seoul, South Korea
5. Department of Obstetrics and Gynecology, College of Medicine, Ewha Womans University, Seoul, South Korea
6. Department of Obstetrics and Gynecology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea
7. Department of Obstetrics and Gynecology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, South Korea
8. Department of Obstetrics and Gynecology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea