[1] Karolinska Inst, Dept Womens & Childrens Hlth, Stockholm, Sweden
[2] Karolinska Inst, Ctr Allergy Res, Stockholm, Sweden
[3] Karolinska Inst, Inst Environm Med, S-10401 Stockholm, Sweden
[4] Univ Gothenburg, Queen Silvia Childrens Hosp, Dept Paediat, Gothenburg, Sweden
[5] Royal Brompton Hosp, Dept Resp Paediat, London SW3 6LY, England
[6] Univ Glasgow, Div Dev Med, Royal Hosp Sick Children, Glasgow, Lanark, Scotland
[7] Univ Oslo, Fac Med, Oslo, Norway
[8] Oslo Univ Hosp, Dept Paediat, Ulleval, Norway
[9] Oslo Univ Hosp, Rikshosp, Oslo, Norway
[10] Salesi Childrens Hosp, Dept Paediat, Ancona, Italy