1. Department of Obstetrics and Gynecology Saitama Medical University Saitama Japan
2. Department of Obstetrics and Gynecology Graduate School of Biomedical Sciences Tokushima University Tokushima Japan
3. Department of Comprehensive Reproductive Medicine Graduate School Tokyo Medical and Dental University Tokyo Japan
4. Umegaoka Women's Clinic Tokyo Japan
5. Department of Obstetrics and Gynecology Graduate School of Medicine Akita University Akita Japan
6. Department of Public Health Graduate School of Medicine The University of Tokyo Tokyo Japan
7. Department of Environmental Health Science and Public Health Akita University Graduate School of Medicine Akita Japan