1. Department of Obstetrics and Gynecology, Sakakibara Heart Institute, Tokyo, Japan;
2. Department of Obstetrics and Gynecology, Mie University School of Medicine, Mie, Japan;
3. Department of Obstetrics and Gynecology, St Marianna University School of Medicine, Kanagawa, Japan;
4. Department of Obstetrics and Gynecology, Hamamatsu University School of Medicine, Hamamatsu, Japan;
5. Department of Obstetrics and Gynecology, Toho University, Tokyo, Japan;
6. Division of Perinatology, Maternal and Perinatal Care Center, Seirei Hamamatsu General Hospital, Hamamatsu, Japan;
7. Department of Obstetrics and Gynecology, Showa University School of Medicine, Tokyo, Japan;
8. Ishiwata Obstetrics and Gynecology Hospital, Ibaraki, Japan;
9. Department of Health Policy, National Center for Child Health and Development, Tokyo, Japan;
10. Department of Diagnostic Pathology, Kindai University Faculty of Medicine, Nara Hospital, Ikoma, Japan;
11. Department of Pathology, Osaka Medical Center and Research Institute for Maternal and Child Health, Izumi, Japan;
12. Department of Perinatology, National Cerebral and Cardiovascular Center, Osaka, Japan