1. Department of Obstetrics and Gynecology, Korea University Guro Hospital, Korea University College of Medicine, Seoul, Korea.
2. Department of Obstetrics and Gynecology, Inha University College of Medicine, Incheon, Korea.
3. Division of Gastroenterology and Hepatology, Department of Internal Medicine, Korea University Guro Hospital, Korea University College of Medicine, Seoul, Korea.
4. Department of Obstetrics and Gynecology, Kyung Hee University College of Medicine, Seoul, Korea.