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Failure to thrive describes the condition of infants and toddlers under age 3 years who have an abnormally low weight for their age and sex. With prolonged and/or severe malnutrition, stature and head circumference can be secondarily affected. The prevalence of failure to thrive is reported to be 10% to 20% of all children treated in ambulatory care centers and up to 5% of all referrals to pediatric hospitals.1 Regardless of specific etiology, failure to thrive may have profound effects on the growing child, including persistent short stature, decreased resistance to infection, and possible developmental impairment and/or disabilities.2,3

Failure to thrive is characterized by insufficient growth recognized by the observation of growth over time using standard growth curves. This entity is also called failure to gain weight, growth failure, and growth faltering. There is a lack of consensus regarding the specific anthropometric criteria required to classify a child as failure to thrive. Thus, many “definitions” for failure to thrive are commonly used. These include: weight less than 3rd percentile, weight-for-height less than 5th percentile, or downward crossing of 2 or more major percentiles on the growth chart. Other definitions include weight 20% or more below ideal weight-for-height, triceps skinfold thickness of 5 mm or less, or a depressed rate of weight gain for age.

Three basic mechanisms underlie failure to thrive: (1) inadequate caloric intake, (2) insufficient utilization or absorption of consumed calories, and (3) increased metabolic requirements. There are numerous specific etiologies for failure to thrive (see Table 30-1). However, most commonly, failure to thrive results from insufficient caloric intake due to either lack of food or feeding and/or behavioral problems that limit a child’s intake. In many cases, a specific organic etiology for a child’s failure to thrive is never identified, and when one is, it rarely presents with growth failure in isolation. Behavioral and psychosocial feeding problems are common and should not be thought of as diagnoses of exclusion.

Table 30-1. Major Etiologies of Failure to Thrive

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