1. Department of Obstetrics and Gynecology, Severance Hospital Yonsei University College of Medicine Seoul Korea
2. Institute of Women's Life Medical Science Yonsei University College of Medicine Seoul Korea
3. Biostatistics Collaboration Unit Yonsei University College of Medicine Seoul Korea
4. Department of Obstetrics & Gynecology, University of Ulsan College of Medicine Asan Medical Center Seoul Korea
5. Department of Obstetrics and Gynecology, Gangnam Severance Hospital Yonsei University College of Medicine Seoul Korea