[1] Univ Toulouse 3, Res Unit Perinatal Epidemiol Child Hlth & Dev, Natl Inst Hlth & Med Res, INSERM U558,Fac Med, F-31073 Toulouse, France
[2] Univ Hosp CHU Toulouse, Epidemiol Serv, Toulouse, France
[3] Natl Inst Publ Hlth, Copenhagen, Denmark
[4] Queens Univ Belfast, Sch Nursing & Midwifery, Belfast, Antrim, North Ireland
[5] Univ Newcastle, Sch Clin Med Sci, Newcastle Upon Tyne, Tyne & Wear, England
[6] Univ Newcastle, Sch Populat & Hlth Sci, Newcastle Upon Tyne, Tyne & Wear, England
[7] Univ Newcastle, Sir James Spence Inst, Newcastle Upon Tyne, Tyne & Wear, England
[8] Univ Hosp Schleswig Holstein, Childrens Hosp, Lubeck, Germany
[9] Gothenburg Univ, Queen Silvia Childrens Hosp, Gothenburg, Sweden
[10] Univ Grenoble 1, Lab Tech Ingn Med & Complexite, Equipe Epidemiol & Methods Clin Res, Grenoble, France
[11] Azienda Sanit Locale Viterbo, Viterbo, Italy
[12] Enable Ireland, Lavanagh Ctr, Cork, Ireland