1. Department of Neurosurgery, Seoul National University Bundang Hospital, Seongnam, Korea.
2. Department of Neurosurgery, Seoul National University College of Medicine, Seoul, Korea.
3. Department of Obstetrics and Gynecology, Seoul National University Bundang Hospital, Seongnam, Korea.
4. Department of Obstetrics and Gynecology, Seoul National University College of Medicine, Seoul, Korea.