1. Department of Obstetrics and Gynecology Niigata University Graduate School of Medical and Dental Sciences Niigata Japan
2. Hospital Care Research Unit Hyogo Prefectural Amagasaki General Medical Center Amagasaki Japan
3. Department of Obstetrics and Gynecology Jichi Medical University, Saitama Medical Center Saitama Japan
4. Centre for Medical Education Nagoya University Graduate School of Medicine Nagoya Japan
5. Fukushima Medical Center for Children and Women School of Medicine, Fukushima Medical University Fukushima Japan