[1] Natl Univ Singapore, Yong Loo Lin Sch Med, Dept Paediat, Singapore 119074, Singapore
[2] Natl Univ Singapore, Yong Loo Lin Sch Med, Dept Obstet & Gynaecol, Singapore 119074, Singapore
[3] Natl Univ Singapore, Yong Loo Lin Sch Med, Dept Neonatol, Singapore 119074, Singapore
[4] Singapore Clin Res Inst Pte Ltd, Singapore, Singapore