1. Department of Obstetrics and Gynecology, Sungkyunkwan University School of Medicine, Samsung Medical Center, Seoul, Korea.
2. Department of Obstetrics and Gynecology, Chung-Ang University College of Medicine, Seoul, Korea.
3. Department of Pediatrics, Sungkyunkwan University School of Medicine, Samsung Medical Center, Seoul, Korea.
4. Department of Pediatrics, School of Medicine, Kyungpook National University, Daegu, Korea.
5. Department of Pathology, Sungkyunkwan University School of Medicine, Samsung Medical Center, Seoul, Korea.
6. Department of Otorhinolaryngology-Head and Neck Surgery, Sungkyunkwan University School of Medicine, Samsung Medical Center, Seoul, Korea.