FETOTOX will include two large Danish birth cohorts; i) the Danish National Birth Cohort (DNBC) of 100,000 enrolled mothers-child pairs, whom has been followed for up to 12 years, and ii) the Aarhus Birth Cohort Biobank (ABCB, ongoing recruitment), and three smaller cohorts from Norway (MISA), Greenland (ACCEPT) and China (CHBC).