[1] Niigata Univ, Grad Sch Med & Dent Sci, Dept Obstet & Gynecol, Niigata 9518510, Japan
[2] Natl Ctr Child Hlth & Dev, Div Fetal Med, Tokyo, Japan
[3] Yamaguchi Univ, Perinatal Care Ctr, Ube, Yamaguchi 755, Japan
[4] Seirei Hamamatsu Gen Hosp, Maternal & Perinatal Care Ctr, Hamamatsu, Shizuoka, Japan
[5] Japan Fetoscopy Grp, Tokyo, Japan