Nutrition for the premature infant following discharge from the neonatal intensive care unit (NICU) varies based on risk factors such as gestational age, birth weight (BW), occurrence of postnatal complications that affect nutrition (such as bowel resection for necrotizing enterocolitis), and the need for specialized nutritional supplementation caused by an inability to take adequate calories resulting from either volume limitation or inability to feed by mouth. Feeding issues are discussed in Chapter 23, and specialized nutritional support is discussed in Chapter 25. This chapter discusses the special postdischarge nutritional needs of infants born <37 weeks gestation.
THE PREMATURE INFANT IN THE NEONATAL INTENSIVE CARE UNIT
The growth of premature infants in the NICU should be similar to in utero growth rates; however, this growth is difficult to achieve due to inability to provide adequate nutrition in the NICU. Premature infants are at high risk of nutrient deficiencies because they do not receive the in utero transfer of nutrients such as protein, iron, and minerals. Over the years, we have learned that early nutrition is important to maintain in utero accretion rates, especially of protein. In addition, premature infants, especially infants <1000 g (extremely low birth weight [ELBW]), are at significant risk for failure to maintain postnatal growth and growth percentiles. Dusick et al (2003) found that although 16% of ELBW infants were born with a birth weight below the 10th percentile, 89% of these infants had weights at 36 weeks that had fallen below the 10th percentile, leading to postnatal growth failure. As in-hospital growth has been linked to improved neurodevelopmental outcomes, it is essential that premature infants receive appropriate nutrition not only in the NICU but postdischarge to assure optimal catch-up growth in the first year of life.
THE PREMATURE INFANT AFTER DISCHARGE
During the NICU course, cumulative energy and protein deficits frequently accrue in infants born at 31 weeks’ gestation or earlier. These deficits tend to worsen when infants are fed a formula designed for healthy full-term infants or if they are fed with unsupplemented breast milk at discharge. Bone mineral content usually is decreased in premature infants after discharge from the hospital, so attention to intake of calcium, phosphorus, and vitamin D is also critical to catch-up bone-mass accretion. The postdischarge options for feeding premature infants depend on the infant’s hospital course and medical history and may include breast milk with or without supplementation with formula or fortification of breast milk. Formula determination is based on gestational age, birth weight, and clinical history but may include postdischarge transitional formula, term infant formula, and more recently available bovine human milk fortifier and premature infant formula. Other factors to be considered include maternal preference, prenatal history, and growth of the infant.
POSTDISCHARGE FEEDING STRATEGIES
Breast milk is recognized by the American Academy of Pediatrics (AAP) Section on Breastfeeding as the optimal nutrition for infants. Breast milk has many significant benefits and is rich in immune factors. Although breast milk is optimal, due to the increased nutritional needs of premature infants, especially infants <1800 g, breast milk may not provide adequate calories, protein, calcium, phosphorus, and vitamins to these infants. Therefore, these infants often require supplementation of breast milk with these nutrients, either as bovine fortifier or supplemental formula feeds. Table 18-1 compares macronutrient and minerals among different postdischarge nutrition regimens fed at 160 mL/kg.
TABLE 18-1Milk and Infant Formula Nutrient Comparison Based on Intake of 160 mL/kg