Early postnatal nutritional requirements of the very preterm infant based on a presentation at the NICHD-AAP workshop on research in neonatology.

Normal fetal nutrition is a useful guide for understanding postnatal nutrition of infants born very preterm. Fetal lipid uptake gradually increases towards term and is primarily used to produce fat in adipose tissue, with essential fatty acid uptake providing necessary structural and functional elements in membranes of cells in the central nervous system. Fetal glucose uptake and utilization rates are nearly twice as high at 23-26 weeks gestation as they are at term, contributing primarily to energy production and glycogen formation. Amino-acid uptake by the fetus is two-to threefold greater at 23-26 weeks gestation than at term and is required to meet the very high fractional protein synthesis and growth rates at this gestational period; amino acids also contribute significantly to fetal energy production. In contrast, after birth most of the very preterm infants are fed more lipid and glucose and less amino acids and protein than they need. Not surprisingly, therefore, very preterm infants accumulate fat but remain relatively growth restricted at term gestational age compared to those infants who grew normally in utero, and this postnatal growth restriction has long-term adverse growth, development, and health consequences. More thorough understanding of the unique nutritional, metabolic, and growth requirements of the normally growing fetus and the very preterm infant, once born, are needed to determine optimal nutritional strategies to improve the outcome of preterm infants.