[1] McMaster Univ, Dept Clin Epidemiol & Biostat, Hamilton, ON, Canada
[2] Childrens Hosp Philadelphia, Div Neonatol, Philadelphia, PA 19104 USA
[3] Univ Penn, Philadelphia, PA 19104 USA
[4] Murdoch Childrens Res Inst, Melbourne, Vic, Australia
[5] Univ Melbourne, Dept Obstet & Gynaecol, Melbourne, Vic, Australia
[6] Univ Melbourne, Dept Paediat, Melbourne, Vic, Australia
[7] Royal Womens Hosp, Melbourne, Vic, Australia
[8] Univ Calgary, Alberta Childrens Hosp, Res Inst Child & Maternal Hlth, Calgary, AB, Canada
[9] Univ Calgary, Dept Pediat, Calgary, AB T2N 1N4, Canada
[10] Univ Calgary, Dept Community Hlth Sci, Calgary, AB T2N 1N4, Canada
[11] Univ British Columbia, Child & Family Res Inst, Vancouver, BC V5Z 1M9, Canada
[12] Univ British Columbia, Dept Pediat, Vancouver, BC V5Z 1M9, Canada
[13] Univ Toronto, Dept Paediat, Toronto, ON M5S 1A1, Canada
[14] James Cook Univ Hosp, Dept Pediat, Middlesbrough, Cleveland, England
[15] Univ Manitoba, Dept Pediat & Child Hlth, Winnipeg, MB R3T 2N2, Canada
[16] McGill Univ, Dept Pediat, Montreal, PQ H3A 2T5, Canada
[17] Univ Montreal, St Justine Univ Hosp, Montreal, PQ, Canada