1. Department of Obstetrics and Gynecology, Niyazaki Medical College, 5200 Kihara, Kiyotake, Miyazaki, 889-1692, Japan;
2. Department of Obsterics and Gynecology and Perinatal Center, Miyazaki medical College, Miyazaki, Japan; and Division of Veterinary Medicine, Department of Agriculture, Kagoshima University, Kagoshima, Japan