1. Department of Obstetrics and Gynecology, Iwate Medical University School of Medicine
2. Department of Obstetrics and Gynecology, Iwate Prefectural Ninohe Hospital
3. Department of Obstetrics and Gynecology, Iwate Prefectural Ofunato Hospital
4. Center for Maternal, Fetal and Neonatal Medicine, Department of Obstetrics and Gynecology, Saitama Medical Center, Saitama Medical University