1. Department of Obstetrics and Gynecology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
2. Department of Obstetrics and Gynecology, Osaka Medical College Graduate School of Medicine, Takatsuki, Osaka, Japan
3. Department of Obstetrics and Gynecology, Osaka City University Graduate School of Medicine, Osaka, Osaka, Japan
4. Department of Obstetrics and Gynecology, Kansai Medical University Graduate School of Medicine, Hirakata, Osaka, Japan
5. Department of Obstetrics and Gynecology, Kindai University Graduate School of Medicine, Sayama, Osaka, Japan
6. Saito Women’s Clinic, Osaka, Japan
7. Obstetrical Gynaecological Society of Osaka, Osaka, Japan