1. Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Severance Hospital, Institute of Women's Medical Life Science, Yonsei University College of Medicine, Seoul, Korea.
2. Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Gangnam Severance Hospital, Institute of Women's Medical Life Science, Yonsei University College of Medicine, Seoul, Korea.