What is failure to thrive?

Definition of Failure to Thrive

Failure to thrive (FTT) is a state of undernutrition in infants and young children characterized by inadequate weight gain or weight loss, typically defined as weight below the 5th percentile for age on standardized growth charts or weight deceleration crossing two major percentile lines. 1, 2

Core Diagnostic Criteria

The condition manifests through several anthropometric patterns that warrant clinical attention:

• Weight is the primary growth parameter affected, falling below the 5th percentile on multiple occasions or showing deceleration that crosses two major percentile lines on growth charts 3, 2
• Linear growth (height/length) and head circumference are typically either unaffected or affected to a lesser degree than weight, distinguishing FTT from other growth disorders 3
• Growth retardation without a known cause in infants and young children represents the clinical presentation, making it one of the leading developmental disorders and a common cause of pediatric hospitalization 1

Underlying Pathophysiology

The mechanism involves a fundamental nutritional imbalance:

• FTT results from inadequate caloric intake, inadequate caloric absorption, or excessive caloric expenditure that creates a state of undernutrition 2
• The condition represents a disequilibrium between requirements and intakes of energy, and macro- and micronutrients, leading to unsatisfactory nutritional status related to poor growth and health 4
• Most cases (the majority) involve inadequate caloric intake caused by behavioral or psychosocial issues rather than organic disease 3, 2

Clinical Context and Terminology

Important nuances exist in how FTT is conceptualized:

• The preferred updated terminology is "growth faltering," though this term can be ambiguous in populations where the clinical phenotype includes inherently low height growth (such as certain skeletal dysplasias) 1
• FTT is most commonly recognized within the first 1-2 years of life, though it may present at any time in childhood 3
• The condition affects 5-10% of children in primary care settings in the United States, making it a frequently encountered clinical problem 2

Important Diagnostic Considerations

Several caveats affect accurate identification:

• No single anthropometric definition is sufficiently sensitive in identifying faltering growth, and using any single indicator has low positive predictive value 4, 2
• A combination of multiple criteria appears more accurate than relying on a single measurement threshold 4
• In specific populations (such as skeletal dysplasias), failure to thrive was often not clearly defined in studies, making comparisons difficult and emphasizing the need for clear definitions using appropriate growth standards 1

Associated Clinical Features

Beyond anthropometric measurements, FTT encompasses broader developmental concerns:

• Delayed development and abnormal behaviors are commonly associated with the condition, particularly in nonorganic FTT 5
• Contributing factors may include feeding difficulties, swallowing dysfunction, gastroesophageal reflux, and various medical conditions affecting multiple organ systems 1
• Long-term sequelae involving all areas of growth, behavior, and development may occur in children suffering from FTT, emphasizing the importance of early detection and intervention 3