1. Department of Pediatrics, Ewha Womans University Medical Center, Ewha Womans University College of Medicine, Seoul, Korea.
2. Department of Occupational and Environment Medicine, Ewha Womans University Medical Center, Ewha Womans University College of Medicine, Seoul, Korea.
3. Department of Obstetrics and Gynecology, Ewha Womans University Medical Center, Ewha Womans University College of Medicine, Seoul, Korea.