The disease process that leads to the development of type 2 diabetes may start in the womb at the very beginning of life. Fetal growth and birth weight are predictive of diabetes risk in later years. This suggests that the factors that influence the rate of fetal growth – and therefore birth weight – may also activate the process that leads to type 2 diabetes in adult life. It is well known that smoking during pregnancy affects fetal growth and often results in babies with a low birth weight. There is also direct evidence that a woman who smokes during pregnancy increases the risk of her child developing type 2 diabetes in later life. Scott M Montgomery reports.