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Failure to thrive (faltering growth)
Failure to thrive is a description, not a diagnosis: weight falling below a low percentile or crossing two major percentile lines; the commonest cause is inadequate caloric intake, so the work-up starts with a dietary history, observation of a feed and a psychosocial assessment — not with many tests.
Why it matters in the exam
The question shows growth charts and asks you to interpret them. When weight falls first and length only later — this is undernutrition (intake, absorption or increased needs). When weight and length fall together and weight is proportionate to length — think of genetic or constitutional short stature, or an endocrine cause. When head circumference falls first — a neurological or genetic cause.
A second point is the order of work-up: most children with failure to thrive do not need many laboratory tests. Start with a food diary, observation of a feed and questions about the family; basic tests include a blood count, electrolytes, renal and liver function, urinalysis, TSH and tTG-IgA with total IgA once the child eats gluten. Admission is reserved for severe undernutrition, suspected neglect or abuse, and failure of outpatient treatment.
Catch-up needs increased intake, usually 120–150 kcal/kg per day based on ideal weight, with close weight follow-up. In severe undernutrition beware of the refeeding syndrome — a fall in phosphate, potassium and magnesium in the first days — so feeding starts gradually and phosphate is checked. A child who gains weight rapidly in hospital without any change in treatment suggests that the problem was intake at home.
Key points
- Failure to thrive = weight falling below a low percentile or crossing two percentile lines.
- The commonest cause: inadequate caloric intake.
- Work-up starts with history, feed observation and social assessment.
- Catch-up: 120–150 kcal/kg per day.
- In severe undernutrition — beware the refeeding syndrome.
Summary table
| Chart pattern | Meaning | Work-up | Approach |
|---|---|---|---|
| Weight falls first, length later | Undernutrition: intake, absorption or increased needs | Food diary, feed observation, basic tests | Caloric enrichment 120–150 kcal/kg per day |
| Weight and length fall together, weight proportionate | Genetic, constitutional or endocrine short stature | Parental heights, bone age, TSH, IGF-1 | According to the cause |
| Head circumference falls first | Neurological or genetic cause | Brain imaging, genetic testing | Neurology and genetics referral |
| Diarrhoea or fatty stools | Malabsorption (coeliac disease, CF, cow's milk allergy) | tTG-IgA with total IgA, sweat test, elastase | Treat the cause |
| Rapid gain in hospital | Inadequate intake at home | Social assessment | Family intervention, consider neglect |
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Sources
- WHO Child Growth Standards, 2006 (in current use) — Weight-for-age and weight-for-length
- AAP Pediatric Nutrition, 8th edition (2019) — Failure to Thrive
- Nelson Textbook of Pediatrics, 22nd edition (2024) — Failure to Thrive (Faltering Growth)
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.