Chapter 15: Failure to Thrive in the NICU Graduate

I. Intensive care and convalescent care

Failure to thrive is usually considered a condition that develops after an infant is discharged from the hospital. However, suboptimal growth is very common in the NICU environment.

1. Definition

   1. Failure to thrive is an outmoded, imprecise term that remains in use only because alternatives such as growth faltering have failed to catch on. Failure to thrive implies a growth rate less than that which should be achieved based on a child's individual genetic potential during typical conditions of health and well-being. Although, there is no agreed definition of failure to thrive, most definitions involve poor rates of growth (typically slow rates of weight gain), combined with lower bodyweight (eg, a weight less than the 3rd centile).

   2. Malnutrition as a diagnosis overlaps with failure to thrive. Several different methods of diagnosis have been used and many divide malnutrition into mild, moderate, and severe.

2. Incidence

   Failure to thrive in the NICU may be better described as extrauterine growth restriction (EUGR) and it is very common in extremely preterm infants, as their nutritional intake during the first several weeks of life is much worse than it would be in utero. With the additional effect of their comorbidities impacting both nutritional intake and energy requirements, inhospital growth of the preterm infant is often poor, and discharge weights below the 10th centile for age are the rule, rather than the exception.

3. Pathophysiology

   The simplest way to consider FTT is as an imbalance between energy intake and energy requirements. FTT can, therefore, result from

   1. Inadequate nutritional intake

   2. Increased nutritional requirements

   3. Increased nutritional losses

4. Risk factors

   1. Extremely low birthweight (ELBW)

   2. Intrauterine growth restriction (IUGR)

   3. Bronchopulmonary dysplasia (BPD)

   4. Necrotizing enterocolitis (NEC, especially surgical)

   5. Infection (both congenital and late onset)

   6. Chromosomal anomaly

   7. Inborn error of metabolism

5. Clinical presentation

   1. Failure to achieve recommended weight gain from birthweight to discharge

      1. Goal weight gain of ≥18 g/kg/d

   2. Failure to achieve recommended increase in head circumference from birth to discharge

      1. Goal increase in head circumference of ≥0.9 cm/wk

6. Diagnosis

   1. Growth charts (Figures 15-1 to 15-5)

      While daily weights are an important measure of fluid status and provide a single point in assessing nutritional status, plotting weight, length, and head circumference on a weekly basis is essential in understanding the overall health and nutrition in the NICU infant.

      1. Fetal-infant growth chart

         • Should be used until gestational age of 50 weeks

      2. CDC growth chart for boys/girls

         • Birth to 36 months

         • Weight, length, and head circumference for age percentiles

         • Plot according to corrected age

   2. If recommended growth is not attained prior to discharge

      1. Assess the infant's diet and take the necessary steps to ensure adequate nutrition support such as increasing protein intake and dietary protein/energy ratio.

      2. Consider further workup for FTT.

7. Management

   1. Infants in the NICU who are unable to grow, despite adequate nutritional support, should undergo a complete diagnostic workup prior to discharge. Consider the following:

      1. Chronic lung disease

      2. Congenital heart disease

      3. Feeding intolerance (fat malabsorption, ...