1. Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
2. Division of Health Insurance Benefit, Ministry of Health and Welfare, Sejong, Korea.
3. Department of Epidemiology, Seoul National University School of Public Health, Seoul, Korea.
4. Department of Obstetrics and Gynecology, CHA University College of Medicine, Seoul, Korea.
5. Global Health Research Center, Inje University Graduate School of Public Health, Seoul, Korea.