1. Department of Obstetrics and Gynecology, Severance Hospital Yonsei University College of Medicine Seoul Republic of Korea
2. Department of Obstetrics and Gynecology, Wonju Severance Christian Hospital Yonsei University College of Medicine Wonju Republic of Korea
3. Department of Obstetrics and Gynecology, Gil Hospital Gachon University College of Medicine Incheon Republic of Korea
4. Institute of Women's Life Medical Science Yonsei University College of Medicine Seoul Republic of Korea