1. Department of Obstetrics and Gynecology, Yonsei University College of Medicine, Seoul, Korea.
2. Department of Pediatrics, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.
3. Department of Obstetrics and Gynecology, Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.
4. Department of Obstetrics and Gynecology, Yongin Severance Hospital, Yonsei University College of Medicine, Yongin-si, Gyunggi-do, Korea.