1. Department of Obstetrics and Gynecology, Fukaya Red Cross Hospital, 5-8-1 Kamishibachonishi, Fukaya City, Saitama 366-0052, Japan
2. Department of Obstetrics and Gynecology, Tatedebari Sato Hospital, 96 Wakamatsucho, Takasaki City, Gunma 370-0836, Japan
3. Department of Pathology, Fukaya Red Cross Hospital, 5-8-1 Kamishibachonishi, Fukaya City, Saitama 366-0052, Japan
4. Department of Obstetrics and Gynecology, Saitama Medical Center, Saitama Medical University, 1981 Kamoda, Kawagoe City, Saitama 350-8550, Japan