[1] Kings Coll Hosp London, Harris Birthright Res Ctr Fetal Med, London SE5 9RS, England
[2] Univ Indonesia, Cipto Mangunkusumo Natl Hosp, Dept Obstet & Gynecol, Jakarta, Indonesia
[3] Showa Univ, Sch Med, Dept Obstet & Gynecol, Tokyo 142, Japan
[4] Univ Bologna, Div Prenatal Med, Dept Histol & Embryol, Bologna, Italy