Failure to Thrive (Faltering Growth)

How failure to thrive is defined

There is no single universal cutoff. Doctors commonly use one or more of:

• weight for age below the 2nd percentile (WHO charts, under 2 years) or 5th percentile (CDC charts, over 2), on repeated measurements
• weight falling across two or more major percentile lines (for example, from the 75th to below the 25th)
• weight for length below the 5th percentile, or BMI for age below the 5th percentile
• in UK practice (NICE), a fall across 1 centile space if birth weight was below the 9th centile, 2 spaces if between the 9th and 91st, or 3 spaces if above the 91st

A single low measurement is not enough. The trend is what counts.

Patterns on the growth chart

Causes

Doctors once divided causes into "organic" (medical disease) and "non-organic" (psychosocial). Most cases now are understood as mixed, so it is more useful to sort causes by mechanism:

Inadequate intake

• breastfeeding problems, incorrect formula preparation
• oral-motor problems: cleft palate, tongue-tie, neurologic conditions
• feeding aversion after painful reflux or medical procedures
• excessive juice or milk in toddlers
• poverty and food insecurity, parental depression, family stress, rarely neglect

Inadequate absorption or excess losses

• vomiting from reflux or pyloric stenosis
• cow's milk protein allergy
• celiac disease
• cystic fibrosis and other causes of pancreatic insufficiency
• inflammatory bowel disease in older children
• chronic diarrhea from infections or short bowel

Increased energy needs or poor use of calories

• congenital heart disease
• chronic lung disease, recurrent infections, HIV
• hyperthyroidism, chronic kidney disease, metabolic disorders
• genetic syndromes

Diagnosis

The history and examination find the cause in most children. Tests rarely find something unexpected if the history and exam are normal.

History and observation

• pregnancy, birth weight, prematurity
• detailed feeding history, ideally a 3-day food diary
• vomiting, stool pattern, breathing during feeds, recurrent infections
• development, family heights, social circumstances
• watching a feed or meal

Examination

• accurate weight, length and head circumference plotted on the right chart
• signs of malnutrition, dysmorphic features, heart murmur, enlarged liver, skin changes, signs of neglect

Tests (targeted)

• first line, when indicated: blood count, electrolytes, kidney and liver function, urinalysis and urine culture, celiac antibodies (once eating gluten), thyroid function
• guided by symptoms: sweat test for cystic fibrosis, stool elastase, echocardiogram, HIV test, genetic tests, bone age X-ray

Treatment

Nutritional rehabilitation

The goal is catch-up growth, which often needs about 1.5 times the usual calorie intake for age:

• infants: support breastfeeding; higher-calorie formula concentrated as directed by the doctor or dietitian (never by adding less water on your own)
• toddlers: 3 meals and 2 to 3 snacks on a schedule; calorie-dense foods; milk limited to about 16 to 24 oz (500 to 700 ml) a day; juice and grazing limited
• vitamin and mineral supplements such as iron, zinc and vitamin D when needed

Treating the cause

For example, hypoallergenic formula for milk allergy, gluten-free diet for celiac disease, pancreatic enzymes for cystic fibrosis, surgery for pyloric stenosis or some heart defects.

Team approach

Pediatricians, dietitians, speech or occupational feeding therapists, social workers and home visiting nurses may all be involved. Support for parental mental health and access to food programs (such as WIC in the US) are part of treatment.

Hospital admission

Needed rarely: for severe malnutrition, dehydration, failure of outpatient treatment, or concern for safety. Refeeding must be gradual in severe malnutrition to avoid refeeding syndrome.

Outlook

Most children with failure to thrive reach normal weight with treatment. Prolonged undernutrition in the first 2 years can leave lasting effects on height, learning and behavior, which is why early identification matters. Regular weight checks, often every 1 to 4 weeks at first, track response. For the parent-facing signs and first steps, see failure to thrive signs.

Frequently asked questions

What is the definition of failure to thrive?

Failure to thrive is inadequate weight gain in a young child, usually defined as weight below the 2nd to 5th percentile on repeated measurements or a drop across two or more major percentile lines on a growth chart. The trend over time matters more than one measurement.

What is the most common cause of failure to thrive?

The most common cause is inadequate calorie intake, often from feeding difficulties, breastfeeding problems, incorrect formula preparation, or family circumstances such as food insecurity. A single underlying disease is found in a minority of children.

What tests are done for failure to thrive?

Many children need few tests. Common ones include a blood count, kidney and liver tests, a urine test, celiac antibodies and thyroid tests. Others, such as a sweat test, stool tests or a heart scan, are done only if symptoms point that way.

What is the difference between organic and nonorganic failure to thrive?

Organic failure to thrive has a medical cause, such as heart disease or celiac disease. Nonorganic means poor intake without disease, often linked to feeding or social problems. Most cases are now recognized as a mix of both, so doctors focus on mechanisms instead.

How long does it take to treat failure to thrive?

Weight usually starts to improve within 2 to 4 weeks of a good feeding plan. Full catch-up can take several months. Children are weighed regularly until they are growing steadily along a healthy curve.