1. Department of Obstetrics; Hokkaido University Graduate School of Medicine; Sapporo Japan
2. Department of Obstetrics and Gynecology; Ehime University Graduate School of Medicine; Matsuyama Japan
3. Department of Obstetrics and Gynecology; Kyoto Rakuwa-kai Hospital; Kyoto Japan
4. Department of Obstetrics and Gynecology; Okayama University Graduate School of Medicine, Dentistry Pharmaceutical Science; Okayama Japan
5. Department of Obstetrics and Gynecology; Kanagawa Children's Medical Center; Yokohama Japan
6. Department of Obstetrics and Gynecology; University of Tsukuba Hospital; Tukuba Japan
7. Department of Obstetrics and Gynecology; Gunma University Hospital; Maebashi Japan
8. Department of Obstetrics and Gynecology; Kyushu University Hospital; Fukuoka Japan
9. Department of Obstetrics and Gynecology; Anjo Kosei Hospital; Anjo Japan