1. Department of Obstetrics and Gynecology, Seoul National University Hospital, Seoul, Korea.
2. Department of Family Medicine, Seoul National University College of Medicine, Seoul, Korea.
3. Department of Family Medicine & Supportive Care Center, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
4. Department of Obstetrics and Gynecology, Seoul National University College of Medicine, Seoul, Korea.
5. Department of Obstetrics and Gynecology, Seoul Metropolitan Government Seoul National University Boramae Medical Center, Seoul, Korea.
6. Health Promotion Center, Seoul National University Hospital, Seoul, Korea.
7. Department of Family Medicine, Asan Medical Center, Seoul, Korea.
8. Department of Obstetrics and Gynecology, Seoul National University Bundang Hospital, Seongnam, Korea.