Adverse factors acting in foetal or early life have been proposed to be causally related to the development of hypertension and glucose intolerance in adult life. This might be caused by the influence of foetal malnutrition and impaired foetal growth. Another explanation would be that genetic factors can cause a chain of events, leading from disease in the mother, to impaired placental function and later development of disease in the offspring. We investigated the pregnancy outcome in male offspring of 368 diabetic and 38 hypertensive mothers, all diagnosed before pregnancy, compared to the offspring of 143254 mothers without a corresponding pre-pregnancy diagnosis. The offspring were reinvestigated at the age of 18 years, at the time of a conscript test for military service. Offspring to diabetic mothers were shorter, but not thinner, and born after a shorter gestational time, than offspring to non-diabetic mothers. The former also showed increased weight and blood pressure at the conscript testing. This supports the notion of a genetic influence on birth variables as well as bodily development in the late adolescence. Thus, not only foetal malnutrition but also genetic programming seem to be factors of importance for the relationship between impaired foetal growth and adult health.