“…This study is part of the HELIX project, which aims to characterize the exposome during early-life and evaluate its relationship to molecular signatures and child health outcomes (Vrijheid et al, 2014). HELIX is based on six European birth cohort studies: BiB (Born in Bradford), United Kingdom (Wright et al, 2013); EDEN (Étude des Déterminants pré et postnatals du développement et de la santé de l'Enfant), France (Heude et al, 2016); INMA (INfancia y Medio Ambiente), Spain (Guxens et al, 2012); KANC (Kaunus Cohort), Lithuania (Grazuleviciene et al, 2009); MoBa (Norwegian Mother and Child Cohort Study), Norway (Magnus et al, 2016); and Rhea, Greece (Chatzi et al, 2017). In this paper we used data from the HELIX subcohort of 1301 mother-child pairs (MoBa (272), KANC (204), BIB (205), EDEN (198), INMA (223) and RHEA (199)) with information on environmental exposures during pregnancy and between 6 and 11 years of age (median 8.1 years; hereafter referred to as "childhood period").…”