1. Department of Obstetrics and Gynecology, National Hospital Organization Kagoshima Medical Center, Kagoshima, Japan.
2. Dozono Medical House, Kagoshima, Japan.
3. Department of Obstetrics and Gynecology, Kagoshima University, Kagoshima, Japan.
4. Department of Anesthesiology, Faculty of Medicine, Kagoshima University, Kagoshima, Japan.