The long-term effects of poor prenatal nutrition are becoming a matter of increasing concern throughout the world. While the consequences of inadequate caloric and/or vitamin intake during pregnancy have been well characterized, in recent years it has become clear that serious long-term adverse effects may also result from gestational nutrient imbalance, even when total caloric intake is more than sufficient to meet the demands of pregnancy. Excessive fat, carbohydrate or protein intake may permanently alter the homeostatic mechanisms in the fetus, predisposing the offspring of affected pregnancies to serious chronic diseases, including cardiovascular disease, diabetes and cancer. This review summarizes the growing literature on this subject, with particular emphasis on the lasting health-related effects of macronutrient imbalance on fetal development.