1. Department of Obstetrics and Gynecology; Saitama Medical University; Saitama
2. Department of Obstetrics and Gynecology; School of Medicine; Juntendo University
3. Division of Cardiology; Cardiovascular Center; Shioda Memorial Hospital; Chiba Japan
4. Department of Obstetrics and Gynecology; Nerima Hikarigaoka Hospital; Tokyo