1 Department of Perinatology and Gynecology, Kagawa University School of Medicine, 1750-1 Ikenobe, Miki, Kagawa, 761-0793, Japan. toshi28@med.kagawa-u.ac.jp.
2 Department of Perinatology and Gynecology, Kagawa University School of Medicine, 1750-1 Ikenobe, Miki, Kagawa, 761-0793, Japan.
3 Department of Obstetrics and Gynecology, Mitoyo General Hospital, 708 Himehama, Toyohama-cho, Kanonji, Kagawa, 769-1695, Japan.