[1] Hosp Sick Children, Child Hlth Evaluat Sci, Toronto, ON, Canada
[2] Hosp Sick Children, Div Paediat Med, Toronto, ON, Canada
[3] Univ Toronto, Dept Paediat, Toronto, ON, Canada
[4] ICES, Toronto, ON, Canada
[5] Univ Toronto, Edwin SH Leong Ctr Healthy Children, Toronto, ON, Canada
[6] Hosp Sick Children, Ontario Child Hlth Support Unit, Clin Trials Unit, Toronto, ON, Canada
[7] Univ Toronto, Dalla Lana Sch Publ Hlth, Toronto, ON, Canada
[8] Sunnybrook Med Ctr, Toronto, ON, Canada
[9] Univ Ottawa, Childrens Hosp Eastern Ontario, Dept Paediat, Ottawa, ON, Canada
[10] McMaster Univ, Hamilton Hlth Sci Ctr, Dept Pediat, Hamilton, ON, Canada
[11] Prov Council Maternal & Child Hlth, Toronto, ON, Canada
[12] Univ Toronto, Lawrence M Bloomberg Fac Nursing, Toronto, ON, Canada
[13] Univ Toronto, Dalla Lana Sch Publ Hlth, Div Biostat, Toronto, ON, Canada
[14] UCL, Dept Stat Sci, London, England
[15] Queens Univ, Sch Rehabil Therapy, Kingston, ON, Canada