Birthweight is known to differ by ethnicity, with South Asian, black African and Caribbean, and Hispanic ethnic groups having lower birthweight on average, when compared with people of white European ethnicity. Birthweight is the most frequently used proxy of fetal growth, and represents the net effect of a host of genetic, physiological and pathophysiological factors. These same ethnic groups that have lower average birthweight also tend to have a higher prevalence of type 2 diabetes in adulthood. It is not unreasonable to propose that the well-established inverse association between birthweight and risk of type 2 diabetes may at least partially contribute to these differences in prevalence of type 2 diabetes between ethnic groups. This hypothesis would rely on the mechanisms that drive the ethnic differences in birthweight aligning with those that modify the risk of type 2 diabetes. In this issue of Diabetologia (DOI: 10.1007/s00125-014-3474-7), Nightingale et al have furthered this field by determining whether ethnic differences in markers of cardio-metabolic risk are consistent with the differences in birthweight in an ethnically diverse cohort of children. The likely contribution of fetal growth to ethnic differences in risk of type 2 diabetes and cardiovascular disease is discussed, particularly in light of the magnitude of the birthweight differences, as are implications for the prevention of type 2 diabetes.