[1] KK Womens & Childrens Hosp, Singapore 229899, Singapore
[2] Univ Melbourne, Dept Obstet & Gynecol, Melbourne, Vic 3010, Australia
[3] Univ Hong Kong, Dept Obstet & Gynecol, Hong Kong, Hong Kong, Peoples R China
[4] Murdoch Childrens Res Inst, Murdoch, WA, Australia
[5] Univ Melbourne, Sch Populat Hlth, Melbourne, Vic 3010, Australia
[6] Natl Taiwan Univ Hosp, Taipei, Taiwan
[7] Merck Res Labs, West Point, PA USA