Most preterm infants fail to grow after birth and end up growth restricted by term. The main reason is inadequate nutrition. From studies of normal fetal growth and development, we have gained important insight into the requirements for such growth and development that could be applied to the preterm infant of the same preterm gestational age. Maintaining normal blood oxygen content values to support the high rates of cellular metabolism and protein synthesis is essential to promote normal rates of growth. Glucose should be supplied at rates that maintain normal fetal glucose concentrations. Normal human fetal development involves considerable body fat deposition, but more emphasis should be placed on providing essential fatty acids to promote membrane development in neural tissue. Amino acid utilization rates based on fetal animal growth data, when scaled to human fetal growth rates, predict amino acid requirements of 3.6–4.8 g//kg/day at ~24–30 weeks gestation. There is a linear correlation between amino acid supply to preterm infants and protein balance, at least through 3 g/kg/day. While energy is required for protein synthesis, above 80–90 non-protein kcal/kg/d, there is no further increase in protein gain for an increase in energy intake. Improved protein and energy intake in preterm infants that more closely matches fetal nutrition is associated with improved brain growth and neurocognitive outcomes. Insulin concentrations that result from such nutrition probably are sufficient for normal growth; insulin infusions do not add more to promote growth than increased amino acid/protein nutrition and produce significant adverse effects.