1. Medical Data Labo, 289-48 Yamasaki, Naka Ward, Okayama 703-8267, Japan
2. Miyake Ofuku Clinic, 393-1 Ofuku, Minami Ward, Okayama 701-0204, Japan
3. Department of Obstetrics and Gynecology, NHO Okayama Medical Center, 1711-1 Tamasu, Kita Ward, Okayama 701-1192, Japan
4. Department of Obstetrics and Gynecology, NHO Nagasaki Medical Center, 2-1001-1 Kubara, Omura 856-8562, Japan
5. Department of Obstetrics and Gynecology, NHO Saga Hospital, 1-20-1 Hinode, Saga 849-8577, Japan
6. Department of Obstetrics and Gynecology, NHO Mie Chuo Medical Center, 2158-5 Hisaimyojincho, Tsu 514-1101, Japan
7. Department of Obstetrics and Gynecology, NHO Higashihiroshima Medical Center, 513 Saijochojike, Higashihiroshima 739-0041, Japan
8. Department of Obstetrics and Gynecology, NHO Kure Medical Center, 3-1 Aoyama, Kure 737-0023, Japan
9. Department of Obstetrics and Gynecology, NHO Kyoto Medical Center, 1-1 Fukasakumukaihata, Kyoto 612-8555, Japan
10. Department of Obstetrics and Gynecology, NHO Shikoku Medical Center for Children and Adults, 2-1-1 Senyucho, Zentsuji 765-8507, Japan
11. Department of Obstetrics and Gynecology, NHO Kokura Medical Center, 10-1 Harugaoka, Kokuraminami Ward, Kitakyushu 802-8533, Japan