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  • Persistent weight loss over time.
  • Growth failure associated with disordered behavior and development.
  • Weight less than third percentile for age.
  • Weight crosses two major percentiles downward over any period of time and continues to fall.
  • Median weight for age of 76%-90% (mild undernutrition), 61%-75% (moderate undernutrition), or <61% (severe undernutrition).

Failure to thrive (FTT) is an old problem that continues to be an important entity for all practitioners who provide care to children. Growth is one of the essential tasks of childhood and is an indication of the child's general health. Growth failure may be the first symptom of serious organ dysfunction. Most frequently, however, growth failure represents inadequate caloric intake. Malnutrition during the critical period of brain growth in early childhood has been linked to delayed motor, cognitive, and social development. Developmental deficits may persist even after nutritional therapy has been instituted.

FTT was first described by Holt in 1897; he describes a group of children who suddenly "ceased to thrive" and became "wasted skeletons" when weaned after the first 4-6 weeks of life. More than 100 years later there is no consensus definition of FTT. Residents and medical students need to be familiar with several definitions of FTT. Practitioners must also recognize the limitations of each definition. Competing definitions of FTT include the following:

  • Persistent weight loss over time. Children should steadily gain weight. Weight loss beyond the setting of an acute illness is pathological. However, the assessment and treatment for FTT need to be addressed before the child has had persistent weight loss.
  • Growth failure associated with disordered behavior and development. This old definition is useful because it reminds the practitioner of the serious sequelae and important alarm features in children with undernutrition. Currently, FTT is more commonly defined by anthropometric guidelines alone.
  • Weight less than the third percentile for age. This is a classic definition. However, this definition includes children with genetic short stature and children whose weight transiently dips beneath the third percentile with an intercurrent illness.
  • Weight crosses two major percentiles downward over any period of time. Thirty percent of normal children will drop two major percentiles within the first 2 years of life as their growth curve shifts to their genetic potential. These healthy children will continue to grow on the adjusted growth curve. Children with FTT do not attain a new curve, but continue to fall. The most accurate assessment for failure to thrive is a calculation of the child's median weight for age. This quick calculation enables the clinician to assess the degree of undernutrition and plan an appropriate course of evaluation and intervention. The median weight for age is determined by the United States Centers for Disease Control and Prevention (CDC) growth charts. The median should not be adjusted for race, ethnicity, or country of origin. Differences in growth are more likely due to inadequate nutrition in specific geographic or economically deprived populations. Determinations of nutritional status are as follows:...

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