Failure to thrive (FTT) is a sign that describes a particular problem, rather than a diagnosis. The term FTT is used to describe instances of growth failure or, more specifically, failure to gain weight appropriately. In more severe cases, linear growth and head circumference also may be affected. A wide variety of medical problems and psychosocial stressors can contribute to FTT (table 1). However, the underlying cause is always "insufficient usable nutrition" .
FTT affects growing children in important ways . Severe malnutrition can cause persistent short stature, secondary immune deficiency, and permanent damage to various parts of the brain and central nervous system . Early identification and expeditious treatment of FTT may help to prevent long-term developmental deficits . (See "Failure to thrive (undernutrition) in children younger than two years: Management", section on 'Prognosis' and "Secondary immunodeficiency due to underlying disease states, environmental exposures, and miscellaneous causes", section on 'Malnutrition'.)
The etiology of FTT and the initial evaluation of children younger than two years with FTT will be described here. The management of FTT in children younger than two years is discussed separately. (See "Failure to thrive (undernutrition) in children younger than two years: Management".)
MEASUREMENT OF GROWTH
Accurate assessment of the child's weight, length, and head circumference is essential. In the child younger than two years, the recumbent length, rather than the standing height, should be obtained. This measure, along with weight, weight for length, and head circumference, should be plotted on a standardized growth chart.
In the United States, two growth charts are available for children younger than two years of age: those developed by the World Health Organization (WHO) (WHO growth standards) and those developed by the Centers for Disease Control and Prevention and National Center for Health Statistics (CDC/NCHS) (CDC growth charts). In September 2010, the CDC recommended that the WHO growth charts be used to assess the growth of children younger than 24 months in the United States . Use of the WHO growth charts will identify fewer children as underweight than use of the CDC growth charts. Additional differences between the WHO and CDC charts are discussed separately. (See "Measurement of growth in children", section on 'Growth standards'.) Both sets of growth charts are provided below: