1. Department of Obstetrics and Gynecology, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea;
2. Department of Obstetrics and Gynecology, CHA Gangnam Medical Center, CHA University, Seoul, Republic of Korea;
3. Department of Obstetrics and Gynecology, Kyung Hee University Hospital at Gangdong, Seoul, Republic of Korea;
4. Department of Obstetrics and Gynecology, School of Medicine, Wonkwang University, Iksan, Republic of Korea;
5. Department of Obstetrics and Gynecology, Ewha Womans University College of Medicine, Seoul, Republic of Korea;
6. Department of Obstetrics and Gynecology, Pusan National University School of Medicine, Busan, Republic of Korea;
7. Department of Obstetrics and Gynecology, Soonchunhyang University Bucheon Hospital, Bucheon, Republic of Korea;
8. Department of Obstetrics and Gynecology, Dongguk University Gyeongju Hospital, Graduate School of Medicine, Dongguk University, Gyeongju, Republic of Korea;
9. Department of Obstetrics and Gynecology, Konkuk University School of Medicine, Seoul, Republic of Korea