It is well known that the dietary protein level influences both the pregnancy process and development of the offspring. Therefore, a study was carried out to determine the effect that different protein percentages: 10%, 4% and 20% in diets administered to rats during pregnancy, had on food efficiency and on the substrates partition between rat dams and their neonates. Experimentation was thus carried out over a period of 21 days (pregnancy) and comparisons were made with well-nourished rats receiving 10% protein (controls) and between one and other group. Moreover, the effect on pregnancy was observed by comparing pregnant rats with non pregnant rats within each dietary situation. Food intake, weight parameters and food efficiency ratio were recorded in adult rats. Weight parameters were also evaluated in newborns. As results revealed, the highest the protein level in the diet, the highest the food efficiency ratio, both in the pregnant group and in the non pregnant group. Weight changes were determined in rat dams and their neonates, as a consequence of the different protein intakes. These also involved alterations in the substrates partition between the mothers and their offspring. Such findings might lead to the retention of substrates by the maternal tissues and, hence, to impairment of neonatal development.