Fetuses of diabetic mothers have markedly different growth rates and develop considerably different body compositions despite all having a mother with diabetes mellitus during her pregnancy. Fetuses of poorly controlled diabetics who have wide swings in meal-associated plasma concentrations of glucose and fatty acids tend to be macrosomic, with large amounts of subcutaneous adipose tissue. Such conditions are most commonly associated with gestational diabetics. In contrast, severely diabetic pregnant women, particularly those with vascular disorders and hypertension, frequently produce smaller placentas that transfer fewer nutrients to the fetus; their fetuses tend to be growth restricted and relatively devoid of skeletal muscle and body fat. To appreciate how such disparate patterns of growth can occur, it is important to understand the basic aspects of nutrient transport to the fetus. In the following discussion, data from a variety of animal models, principally sheep, are used to augment and support the more limited information from humans.