[1] Chinese Univ Hong Kong, Dept Obstet & Gynaecol, Prince Wales Hosp, Shatin, Hong Kong, Peoples R China
[2] Univ Oxford, John Radcliffe Hosp, Nuffield Dept Obstet & Gynaecol, Oxford OX3 9DU, England
[3] Dana Farber Canc Inst, Dept Pediat Oncol, Boston, MA 02115 USA
[4] Harvard Univ, Childrens Hosp, Sch Med, Boston, MA 02115 USA
[5] Harvard Univ, Childrens Hosp, Vasc Biol Program, Dept Surg,Med Sch, Boston, MA 02115 USA
[6] Chinese Univ Hong Kong, Sch Biomed Sci, Shatin, Hong Kong, Peoples R China