[1] Lovisenberg Diaconal Univ Coll, Dept Postgrad Studies, Oslo, Norway
[2] Univ Oslo, Inst Clin Med, Med Fac, Oslo, Norway
[3] Oslo Univ Hosp, Dept Neonatal Intens Care, Div Pediat & Adolescent Med, Oslo, Norway
[4] Oslo Univ Hosp, Norwegian Neonatal Network, Oslo, Norway
[5] Oslo Ctr Biostat & Epidemiol, Res Support Serv, Oslo, Norway
[6] Oslo Metropolitan Univ, Fac Hlth Sci, Oslo, Norway
[7] Ostfold Univ Coll, Dept Hlth & Welf, Halden, Norway
[8] Ostfold Hosp Trust, Dept Internal Med, Kalnes, Norway
[9] Sorlandet Hosp Trust, Dept Pediat & Adolescent Med, Kristiansand, Norway
[10] More & Romsdal Hosp Trust, Dept Paediat, Alesund, Norway
[11] Norwegian Univ Sci & Technol, Clin Res Unit, Trondheim, Norway
[12] Univ Tromso, Fac Hlth Sci, Tromso, Norway
[13] Univ Hosp North Norway, Dept Pediat, Tromso, Norway
[14] Akershus Univ Hosp, Dept Pediat & Adolescent Med, Lorenskog, Norway
[15] Haukeland Hosp, Neonatal Intens Care Unit, Dept Pediat, Bergen, Norway
[16] Stavanger Univ Hosp, Dept Paediat, Stavanger, Norway
[17] Univ Stavanger, Fac Hlth Sci, Stavanger, Norway
[18] Ostfold Cty Hosp, Dept Pediat & Adolescent Med, Gralum, Norway
[19] Vestfold Hosp Trust, Dept Paediat, Tonsberg, Norway
[20] Oslo Univ Hosp, Dept Paediat Res, Oslo, Norway
[21] Trondheim Reg & Univ Hosp, St Olavs Hosp, Dept Paediat, Trondheim, Norway
[22] Norwegian Univ Sci & Technol, Dept Clin & Mol Med, Trondheim, Norway
[23] Inst Clin Med, Res Grp Clin Neonatal Med & Epidemiol, Oslo, Norway