[1] Seoul National University College of Medicine,Department of Obstetrics and Gynecology
[2] Seoul National University Bundang Hospital,Department of Obstetrics and Gynecology
[3] Dankook University College of Medicine,Department of Obstetrics and Gynecology, Cheil General Hospital and Women’s Healthcare Center
[4] Ajou University Medical School,Department of Obstetrics and Gynecology
[5] Inha University Hospital,Department of Prevention and Management
[6] Inha University,School of Medicine
[7] Seoul Metropolitan Government Seoul National University Boramae Medical Center,Department of Biostatistics