1. Department of Obstetrics and Gynecology, Konkuk Medical Center, Konkuk University School of Medicine, Seoul, Korea.
2. Department of Obstetrics and Gynecology, Korea University Anam Medical Center, Korea University College of Medicine, Seoul, Korea.
3. Department of Obstetrics and Gynecology, Cha University Ilsan Medical Center, Goyang, Korea.
4. Department of Obstetrics and Gynecology, Sanggye Paik Hospital, Inje University College of Medicine, Seoul, Korea.
5. Department of Pediatrics, Konkuk Medical Center, Konkuk University School of Medicine, Seoul, Korea.