Neonatal Nutrition Assessment

KEY POINTS

• 1.

  All infants should be classified at birth with the use of appropriate anthropometric measurement techniques to determine risk status for complications such as hypoglycemia or catabolism. Growth charts and tools to determine z -scores are readily available and should be used.

• 2.

  Hospitalized infants are at higher risk for growth impairment, so patterns on a growth chart and growth velocity throughout hospitalization should be routinely monitored as part of standard clinical care.

• 3.

  A nutrition-focused physical examination includes anthropometric assessments, vital signs, and careful assessment for any evidence of nutritional deficiencies.

• 4.

  Controversy exists regarding frequency and timing of biochemical monitoring for common complications of prematurity, such as metabolic bone disease and cholestasis. Clinicians should consider adopting a standardized approach that incorporates expert opinion when evidence is lacking.

• 5.

  All high-risk infants should have daily assessment of nutrient intake.

• 6.

  A registered dietitian should be part of the healthcare team to assess neonatal growth and nutrient intakes.

Introduction

Growth is a normal state for infants and an indicator of wellness. All infants deserve personalized nutritional care that will promote growth and a healthy start to life. Nutritional assessment based on growth history; biochemical, clinical, and physical parameters; and nutritional intake can allow the clinician to determine which infants are not growing well and/or have not achieved adequate nutrition.

Preterm and critically ill infants need focused growth monitoring, because nutrient needs are not based on the cues from the infant but have to be estimated and delivered by the medical team. In this chapter, we seek to describe clinically available tools and the highest-quality evidence available to assess neonatal nutritional status. Further information on parenteral and enteral nutrition is included in separate chapters focused on nutrition requirements.

Classification of the Newborn

Newborn assessment and anthropometric classification at the time of delivery reflect intrauterine growth and allow identification of infants who are at higher nutrition risk. Many of these small- and large-for-gestational age (SGA and LGA) infants are also at risk of early metabolic complications such as hypoglycemia in the first days of life. SGA infants often have low glycogen stores, whereas many LGA infants may be at risk of abnormal glucose levels due to maladaptation to higher glucose loads from uncontrolled maternal diabetes. Symptoms of hypoglycemia include jitteriness, poor feeding, tachypnea, floppy tone, and even seizures. In subsequent days, these early metabolic abnormalities may resolve, but multiple studies have shown these infants to also be at risk of abnormal growth trajectories ( Chapter 19 , 20 ).

Birth Weight Classification

• Per Centers for Disease Control and Prevention 2019 data, about 8.3% of all infants have a birth weight of less than 2500 g and are categorized as low birth weight (LBW). ^, Those born with a birth weight of less than 1500 g are identified as very low birth weight (VLBW) infants, which is about 1.4% of all infants. Less than 1% of infants are born with a weight of less than 1000 g and are categorized as extremely low birth weight (ELBW).

• Birth weight may reflect the adequacy of nutritional stores, such as those of protein, fat, iron, calcium, phosphorus, and other important nutrients.

• Higher gestational age reflects maturity with better ability to tolerate fluctuations in biochemical levels of various nutrients. Adjusting age for prematurity assists in setting expectations for developmental achievements.

• Premature birth is the most common cause of low birth weight. We have nutritional guidelines for VLBW, preterm infants that aim to meet the metabolic and growth needs and achieve growth rates similar to those in utero. ^,

• Besides prematurity, another important cause of low birth weight is fetal or intrauterine growth restriction (IUGR). At any gestation, infants may be classified as SGA (birth weight < the 10th percentile), appropriate for gestational age (AGA), or LGA (birth weight > the 90th percentile). Based on these definitions, 20% of the population is expected to have a birth weight outside the AGA category. Not all infants who meet criteria to be labeled SGA or LGA are medically compromised, nor have they suffered from an obvious intrauterine insult that may explain their abnormal growth. Some conditions are definitely more frequent in the LGA and SGA categories, but it is important to understand that these definitions are statistical and somewhat arbitrary, and therefore, not everyone in these categories has ongoing pathology. Many of these infants have weights that are normal, healthy metrics for their genetic profiles. In some infants, IUGR may also be due to maternal factors that did not support in utero growth at their genetic potential. These infants also may not have intrinsic abnormalities.

• Newer technologies can often allow the identification of the cause for IUGR. Many fetuses are growth restricted because of compromised fetal blood flow; the Doppler waveform of blood flow in the umbilical vessels can provide useful information. ^, Similarly, magnetic resonance imaging of whole-body fetal adipose tissue can also provide useful information to aid assessment of fetal growth and placental sufficiency.

Features of Fetal Growth Restriction

• Can be identified via prenatal ultrasound or by physical exam at birth

• Thin, wasted appearance on prenatal imaging and after birth

• Deficiency of subcutaneous tissue and muscle, noted in the cheeks, neck and chin, arms, back, buttocks, legs, and trunk

• Cranial sutures may be widened, and the umbilical cord may be thin and lacking in Wharton’s jelly

• Dysmorphic features could indicate a congenital syndrome

One scoring system is the Clinical Assessment of Nutritional Status (CANS) ( Fig. 22.1 ). The intent of this exam is to distinguish a term infant who suffered from fetal malnutrition from an infant who is simply physiologically small for gestational age. This malnutrition might result in altered body composition and impaired neurodevelopmental potential. The signs of malnutrition include:

• Hair: silky versus straight

• “Staring” or flag sign

• Reduced buccal fat in the cheeks

• Sharply defined thin chin or fat double chin

• A thin, clearly evident neck with loose, wrinkled skin

• “Accordion” pleating of the skin of arms and legs with loose, easily lifted skin over major joints

• Loss of subcutaneous fat on the back with skin easily lifted

• Minimal fat and wrinkled skin over abdomen

• Buttocks with deep folds

This CANS simple scoring system was developed for term infants and is intended to be used in the first 48 hours of life. ^, Some researchers then applied the CANSCORE to preterm infants. They found that maternal hypertension and preeclampsia, oligohydramnios, disturbed umbilical artery Doppler flow, neonatal hypoglycemia, polycythemia, feeding intolerance, and necrotizing enterocolitis were all associated with what was described as fetal malnutrition. Interestingly, not all of the infants who were identified as having had fetal malnutrition were classified as SGA based on anthropometrics. We clearly need ways for more accurate identification of the predisposing factors and validation of the CANSCORE for preterm infants.

LGA infants can be born to constitutionally tall parents or to mothers with uncontrolled diabetes or obesity. ^, Infants of diabetic mothers may have increased adiposity resulting from storage of the fat generated from the conversion of high glucose supply from the hyperglycemic mothers. These fat stores may be visually obvious to the examiner and can also be objectively identified by measuring body composition, using indices such as an elevated weight, mid-upper arm circumference, and/or triceps skinfold thickness in the absence of an elevated length and head circumference. During the early neonatal period, infants of diabetic mothers are important to identify because they are at higher risk for hypoglycemia, hypocalcemia, polycythemia, and congenital malformations.

Anthropometric and Growth Assessment