Associations between circulating sex hormones in blood serum and DNA methylation have previously been found in ALSPAC children in both childhood and adolescence. Such associations may tag biological pathways involved in endocrine-related diseases, with important implications for the study of hypo- or hyper- gonadism, as well as various metabolic disorders known to be regulated by sex hormones. Whether such associations also exist between maternal levels of sex hormones and the mothers growing foetus is not known. The project will look at the effects of sex hormones in mothers on DNA methylation in children, using both observational and genetic evidence. Maternal sex hormone genotype will be used as a proxy of circulating sex hormone levels in genetic analyses enabling true causal associations to be unpicked from those due to confounding. Paternal genotype will be used as negative control to determine whether associations are due to in utero exposure to maternal sex hormones or simply shared genotype between mother and offspring.