1. Department of Obstetrics and Gynecology, College of Medicine, Ewha Womans University, Seoul, Korea.
2. Healthcare System Gangnam Center, Seoul National University Hospital, Seoul, Korea.
3. Department of Internal Medicine, College of Medicine, Ewha Womans University, Seoul, Korea.
4. Department of Occupational and Environmental Medicine, College of Medicine, Ewha Womans University, Seoul, Korea.