[1] Ottawa Hosp, Res Inst, Clin Epidemiol Program, Ottawa, ON K1H 8L6, Canada
[2] Univ Ottawa, Dept Med, Ottawa, ON, Canada
[3] Childrens Hosp Eastern Ontario, Ottawa, ON K1H 8L1, Canada
[4] Univ Ottawa, Dept Epidemiol & Community Med, Ottawa, ON, Canada
[5] Univ British Columbia, Dept Pediat, Childrens & Womens Hlth Ctr British Columbia, Vancouver, BC V6T 1W5, Canada
[6] Univ British Columbia, Div Hematopathol, Childrens & Womens Hlth Ctr British Columbia, Vancouver, BC V5Z 1M9, Canada
[7] Univ British Columbia, Dept Pathol & Lab Med, Vancouver, BC V5Z 1M9, Canada
[8] Royal Univ Hosp, Dept Neonatol, Saskatoon, SK S7N 0W8, Canada
[9] Univ Saskatchewan, Saskatoon, SK, Canada
[10] McMaster Univ, Dept Pathol & Med, Hamilton, ON, Canada
[11] McGill Univ, Jewish Gen Hosp, Dept Neonatol, Montreal, PQ H3T 1E2, Canada
[12] McGill Univ, Dept Med, Montreal, PQ, Canada
[13] McGill Univ, Dept Epidemiol Biostat & Occupat Hlth, Montreal, PQ, Canada
[14] CHU St Justine, Dept Neonatal, Montreal, PQ, Canada
[15] Univ Montreal, Montreal, PQ, Canada
[16] Univ Toronto, Mt Sinai Hosp, Samuel Lunenfeld Res Inst, MiCare Res Ctr,Inst Human Dev,Canadian Inst Hlth, Toronto, ON M5G 1X5, Canada
[17] Hosp Sick Children, Toronto, ON M5G 1X8, Canada
[18] Univ Western Ontario, St Josephs Healthcare, London, ON, Canada
[19] Univ Western Ontario, London Hlth Sci Ctr, London, ON, Canada
[20] Univ Western Ontario, Schulich Sch Med & Dent, London, ON, Canada