Unfortunately, premature birth occurs commonly in the United States. Improving the survival of very low-birth-weight (VLBW) infants depends in large part upon understanding the physiologic capabilities of their immature organ systems and providing appropriate support as they mature. Advances in the nutritional support of these infants have contributed to the better outcomes we have come to expect today, even for the smallest infants. In this review, we will discuss the limitations of gastrointestinal function and the unique nutritional requirements of very low-birth-weight infants and describe the current methods of enteral and parenteral nutrition support used to meet these requirements.
By 24 to 26 weeks of gestation, the fetal gastrointestinal tract is morphologically similar to that of the full-term infant; however, functional development is far from complete. Maturation of gastrointestinal motility, digestion, and absorption continues through much of the first year of life, even in full-term infants, as a result of an interplay between the preprogrammed "biological clock" and environmental influences. The decision to feed the VLBW infant must take into account the developmental limitations as well as the potential for enhancing intestinal maturation at each stage of development (Table 1).
Fetal swallowing is evident at the beginning of the second trimester.