1. Department of Pediatrics, Kyung Hee University School of Medicine, Seoul, Korea.
2. Department of Obstetrics and Gynecology, Kyung Hee University School of Medicine, Seoul, Korea.
3. Department of Obstetrics and Gynecology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
4. Department of Obstetrics and Gynecology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.