Europe is facing a rapidly growing threat from Type 2 diabetes mellitus (T2D), which is undoubtedly associated with an unhealthy diet and a more sedentary lifestyle. Evidence is accumulating that gestational diabetes mellitus (GDM) may be playing a role in this process. Thus it provides a significant opportunity for preventing future T2D. Not only is GDM prevalence on the rise, but intrauterine exposure to hyperglycaemia predisposes the offspring to diabetes and obesity. Another putative contributing factor is a low vitamin D status, which is also increasing in prevalence and may have causal links with both obesity and decreased glucose tolerance. The main aims of this project are: 1) to establish the current status of the prevalence of GDM in Europe and facilitate the adoption of a single diagnostic approach and 2) to deliver the best strategy that prevents GDM. The latter was deemed as not fully feasible within the scope of this call and our decision was to test the most relevant approaches (diet, exercise, vitamin D, alone or in combination) against surrogate variables of GDM (fasting blood glucose, insulin sensitivity, pregnancy weight gain) to come up with the best intervention for entry into a definitive GDM prevention trial. Deliverables include the sample size and modus operandi for such a trial. Value will be added to the project by 1) Assessing variables modifying the uptake of preventive interventions, 2) Exploring health costs of GDM and potential savings of preventive approaches, 3) Improving pathophysiological understanding by assessing intervention effect on several parameters in mother and foetus and 4) Facilitating future research through a well defined cohort of mother-offspring pairs and comprehensive biobanking.