1. Department of Radiation Oncology, Asan Medical Center, University of Ulsan, College of Medicine, Seoul, Republic of Korea
2. Department of Obstetrics and Gynecology, Asan Medical Center, University of Ulsan, College of Medicine, Seoul, Republic of Korea
3. Department of Clinical Epidemiology and Biostatistics, Asan Medical Center, University of Ulsan, College of Medicine, Seoul, Republic of Korea