Anthropometrics. Serial measurements of weight, length, and head circumference allow for evaluation of growth patterns.
Weight. During the first week of life, weight loss of 10–20% of birthweight is expected because of changes in body water compartments. Preterm infants lose more weight and regain birthweight slower than term infants. Weight gain generally begins by the second week of life. Average daily weight gain based on normal intrauterine growth is 10–20 g/kg/day (1–3% of body weight/day). Infants should be weighed daily.
Length. Length is a better indicator of lean body mass and long-term growth and is not influenced by fluid status. Weekly assessment is recommended. Average length gain in preterm infants is 0.8–1.0 cm/week, whereas term infants average 0.69–0.75 cm/ week.
Head circumference. Intrauterine head growth is 0.5–0.8 cm/week. This is used as an indicator of brain growth. Premature infants exhibit catchup growth in head circumference that may exceed normal growth rate, but an increase in head circumference >1.25 cm/week may be abnormal and associated with hydrocephalus or intraventricular hemorrhage.
Weight for length can be used to determine symmetry of growth. Current weight expressed as a percentage of ideal weight for length can identify infants at risk for under- or overnutrition. Catchup growth occurs faster if only weight is lagging compared to length and head circumference. Weight gain is slower in large for gestational age infants.
Measurements of weight, length, and head circumference are plotted on growth charts to facilitate comparison to established norms. This can help to identify special needs.
Growth charts provide longitudinal assessment of an infant's growth. Growth charts for term boys and girls are available from the Centers for Disease Control (www.cdc.gov/growthcharts). Two types of charts exist for very low birthweight (VLBW) infants: those based on intrauterine growth or those based on postnatal growth. Assessment of postnatal growth failure is better reflected on postnatal growth charts. Variations exist in the reference populations for the various growth charts. Normal growth customarily falls between the 10th and 90th percentiles when adjusted for gestational age. Intrauterine growth is classified as appropriate for gestational age; large for gestational age (eg, infants of diabetic mothers, postmature infants, or infants with Beckwith-Wiedemann syndrome) or small for gestational age.
To maintain weight, give 50–60 kcal/kg/day (60 nonprotein kcal/kg/day).
To induce weight gain, give 100–120 kcal/kg/day to a term infant (gain: 15–30 g/ day) and 110–140 kcal/kg/day to a premature infant (70–90 nonprotein kcal/kg/day). Growth in premature infants is assumed to be adequate when it approximates the intrauterine rate (ie, 15 g/kg/day).
Carbohydrates. Approximately 10–30 g/kg/day (7.5–15g/kg/day) are needed to provide 40–50% of total calories. Lesser amounts of carbohydrates should provide total energy requirements in infants with chronic lung disease.
Proteins. Adequate protein intake has been estimated at 2.25–4.0 g/kg/day (7–16% of total calories, or 2–3 g/100 kcal for efficient utilization). Protein intake in low birthweight infants should not exceed 4.0 g/kg/day.
Fats. Fat requirements are 5–7 g/kg/day (limit: 40–55% of total calories or ketosis ...
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