1. Korean Motherisk Program, Seoul, Korea.
2. Department of Obstetrics and Gynecology, Cheil General Hospital and Women's Healthcare Center, Dankook University College of Medicine, Seoul, Korea.
3. Department of Obstetrics and Gynecology, Ilsin Christian Hospital, Busan, Korea.
4. Department of Obstetrics and Gynecology, Miz Women's Hospital, Daejeon, Korea.
5. Department of Obstetrics and Gynecology, Mam's Women's Hospital, Ulsan, Korea.