1. Department of Obstetrics and Gynecology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan
2. Department of Regenerative Science, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, 2-5-1 Shikatacho, Kita-ku, Okayama-shi, Okayama 700-8558, Japan
3. Department of Obstetrics and Gynecology, Tokyo Saiseikai Central Hospital, 1-4-17 Mita, Minato-ku, Tokyo 108-0073, Japan
4. HM Ladies Clinic Ginza, 3-4-16 Ginza, Chuo-ku, Tokyo 104-0061, Japan