The Northern Finland Birth Cohort Project (NFBC, www.kelo.oulu.fi/NFBC), Avon Longitudinal Study on Parents and Children (ALSPAC) and other projects have identified several characteristics of the foetal environment (e.g. parental stress, smoking/drinking, obesity, excessive weight gain and other complications during pregnancy) that impact on intrauterine growth, preterm birth, the hypothalamo-pituitary-adrenal (HPA) axis, neonatal health and later morbidity. In the present proposal we will focus in one of the most important complications of pregnancy, gestational diabetes mellitus (GDM), a feasible "test exposure" because of complexities and unpredictable problems in these analyses, while proposing to create a more extensive data resource for future analyses of e.g. gestational hypertensive disorders, stress, obesity and weight gain during pregnancy as a collaborative effort. Intrauterine period is highly susceptible for the impact of environment. Epigenetic changes play likely a key role also in normal development.