1. Department of Obstetrics and Gynaecology, Saitama Medical University Saitama Medical Centre, Saitama, Japan
2. Social Insurance Yokohama Central Hospital, Kanagawa, Japan
3. Department of Obstetrics and Gynaecology, Tokyo Women's Medical University Medical Centre East, Tokyo, Japan
4. Department of Obstetrics and Gynaecology, Maternal and Child Health Centre, Aiiku Hospital, Tokyo, Japan
5. Department of Obstetrics and Gynaecology, Juntendo University School of Medicine, Tokyo, Japan
6. Department of Obstetrics and Gynaecology, Juntendo University Urayasu Hospital, Chiba, Japan
7. Koshigaya Municipal Hospital, Saitama, Japan
8. Miyazaki University Hospital, Miyazaki, Japan
9. Department of Obstetrics and Gynaecology, Hamamatsu University School of Medicine, Shizuoka, Japan
10. Kanzaki Ladies Clinic, Hyougo, Japan
11. Department of Health Sciences, School of Medicine, Hokkaido University, Hokkaido, Japan
12. Department of Obstetrics and Gynaecology, Tokyo Women's Medical University, Tokyo, Japan