Supported by the National Institute of Environmental Health Sciences (R21ES029681; R01ES030691, R01ES029944, R01ES030364, R21ES028903, and P30ES007048, to L.C.; R01ES030691, R01ES030364, R21ES028903, and P30ES007048, to R.M.; R01ES030691, R01ES029944, R01ES030364, and P30ES007048, to D.V.C.; R01ES030691, R01ES029944, R01ES030364, and R21ES028903, to D.V.; R01ES030364, to N.S.; and P30ES007048, to E.G), the National Institutes of Health (P01CA196569 and R01CA140561, to D.V.C.; P30DK048522, to N.S.), the Instituto de Salud Carlos III (Ministry of Economy and Competitiveness) (MS16/00128, to M.C.), and the Juan de la Cierva-Incorporacion fellowship (IJC2018-035394-I, to L.M.), awarded by the Spanish Ministerio de Economia, Industria y Competitividad. The Human Early Life Exposome project was supported by the European Community’s Seventh Framework Programme (FP7/2007-2013, under grant 30833). INMA data collections were supported by grants from the Instituto de Salud Carlos III, CIBERESP, and the Generalitat de Catalunya-CIRIT. The KANC cohort was supported by the Lithuanian Agency for Science Innovation and Technology (31V-77). For a full list of funding that supported the EDEN cohort, see https://doi.org/10.1093/ije/dyv151. The Norwegian Mother, Father and Child Cohort Study was supported by the Norwegian Ministry of Health and Care Services and the Ministry of Education and Research. The Rhea cohort was supported by European projects; the Greek Ministry of Health (Program of Prevention of Obesity and Neurodevelopmental Disorders in Preschool Children, in Heraklion district, Crete, Greece), 2011-2014; and Rhea Plus: Primary Prevention Program of Environmental Risk Factors for Reproductive Health, and Child Health: 2012-2015. The BiB cohort was supported by a Wellcome Trust infrastructure grant (WT101597MA). R.R.C.M. and J.W. received funding from the National Institute for Health Research Applied Research Collaboration for Yorkshire and Humber. The CRG/UPF Proteomics Unit is part of the Spanish Infrastructure for Omics Technologies (ICTS OmicsTech) and a member of the ProteoRed PRB3 consortium, which is supported by grant PT17/0019 of the PE I + D+i 2013-2016 from the Instituto de Salud Carlos III and European Regional Development Fund. This study was further supported by grants from the Spanish Ministry of Science, Innovation and Universities, Centro de Excelencia Severo Ochoa 2013-2017 (SEV-2012-0208), and Secretaria d’Universitats i Recerca del Departament d’Economia i Coneixement de la Generalitat de Catalunya (2017SGR595).