ABSTRACT
The extent of fetal growth and infant size at birth result from underlying genetics as well as in utero exposures that include nutrient availability. The placenta is a unique organ that mediates the inuence of maternal nutrient status on nutrient delivery to the fetus. Alterations in maternal nutrient availability such as nutrient decit or excess impact placental transport of nutrients and, therefore, the growth of the fetus. In this chapter, we describe two well-studied placental amino acid (AA) transport systems, System A and System L, and how maternal nutritional status impacts the expression and activity of these transporters. Research to date has established a clear, mechanistic relationship between maternal nutrient deciency such as overall calorie restriction or protein restriction during pregnancy and reductions in AA transport mediated by System A and System L. On the other side of the spectrum, research into maternal overnutrition, either through maternal obesity, gestational diabetes, or dietary fat excess, has produced more variable ndings, therefore supporting a call for further research into the role of placental AA transport in pregnancies experiencing nutrient excess and fetal overgrowth.
