1. Department of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
2. Department of Obstetrics and Gynecology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
3. Division of Pediatric Infectious Diseases, Department of Pediatrics, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
4. Department of Neonatology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.