Failure to thrive and faltering growth

• Faltering growth, formerly called failure to thrive, means a child is gaining weight more slowly than expected for age and sex; it is a clinical observation, not a diagnosis by itself. ^{[1] [2]}
• The modern approach is centile-based and repeated measurements over time: a fall across two weight centile spaces in a child whose birth weight was between the 9th and 91st centiles, or weight below the 2nd centile, should make you look hard. ^[1]
• Most children who falter are simply not taking in enough calories; absorption problems and high metabolic demands are less common but important. ^{[4] [5]}
• The strongest tool is a careful feeding and social history, plus a single set of growth measurements converted to a z score. ^{[1] [5]}
• Most children are managed in primary care with relaxed, calorie-dense feeding, good sleep and follow-up; hospitalisation and extensive testing are usually unnecessary. ^{[4] [5]}

By the end of this page you should be able to:

1. State why faltering growth is preferred to "failure to thrive", and how a fall across centiles is defined. ^{[1] [2]}
2. Recognise the three mechanisms of undernutrition and list the common conditions in each. ^{[4] [5]}
3. Generate a focused feeding, medical, family and social history from the parents or carers. ^{[1] [5]}
4. Interpret weight-for-age, weight-for-length or height and BMI z scores using WHO or CDC charts. ^{[3] [5]}
5. Decide which investigations are worth doing, and when a child should be referred or admitted. ^{[1] [5]}
6. Outline outpatient nutrition support, including catch-up calories and monitoring. ^{[4] [5]}

This page covers slow weight gain in infants and children: how it is recognised, why it happens, how it is assessed, and what to do about it. The condition is called faltering growth in current UK guidance, although older literature and many US sources still use failure to thrive. ^{[1] [2]} NICE guideline NG75, published on 27 September 2017, provides the centile-based thresholds and the practical assessment steps used on this page, and says plainly that neglect is an uncommon explanation. ^{[1] [2]} The American Academy of Pediatrics and AAFP literature give the useful US framework of z scores and hospitalisation indications. ^{[4] [5]}

For growth monitoring, the WHO Child Growth Standards, based on the Multicentre Growth Reference Study in six countries and published in April 2006, describe how children should grow between 0 and 60 months under optimal conditions, including WHO recommendations for breastfeeding. ^[3] They are used for children under 2 years, and CDC growth charts are used for children aged 2 to 20 years. ^{[4] [5] [1]}

A fall across centiles often reflects undernutrition: the child's nutritional intake is not meeting the body's energy need. ^[2] Weight is the first parameter affected, followed by length or height, then head circumference in very severe or prolonged cases. ^[4] In practice you are usually looking at weight-for-age, weight-for-length or height, and, in older children, body mass index. ^[5]

There is no single cut-off that makes a child "failure to thrive", which is one reason the preferred term is now faltering growth. ^[4] What sounds like a dramatic label can simply be a small, slowly growing constitutional child or a premature infant catching up on a different trajectory. ^[2] The question is not which centile the child sits on today, but whether the trend over several measurements is wrong.

NICE NG75 offers centile-based thresholds for concern after the early days of life. ^[1] A centile space is the gap between adjacent centile lines on the UK WHO charts. ^[1]

Two important points sit underneath that table. First, NICE also flags a length or height centile more than 2 centile spaces below the mid-parental centile as suggestive of undernutrition or of a primary growth disorder. ^[1] Second, when the child is over 2 years of age, calculate the BMI centile: below the 2nd centile may reflect either undernutrition or a small build, while below the 0.4th centile suggests probable undernutrition needing assessment and intervention. ^[1]

US practice uses a slightly different emphasis. A child whose weight is below the 5th percentile for sex and corrected age, or whose weight-for-length is below the 5th percentile, or whose BMI-for-age is below the 5th percentile, will commonly be labelled with growth faltering. ^[4] A sustained fall by two major percentiles is also used. ^[4] More recently, z scores have been favoured: a modified z score between minus 3 and plus 3, where more negative values mean more severe malnutrition; a z score falling by 1 or more is worrying unless the fall is compensatory, such as a large-for-gestational-age newborn settling towards their canalised curve. ^[5]

These different definitions are saying the same thing in different dialects, and that is why every clinic should agree which one it uses.

Weight loss after birth is expected. NICE recommends that an infant who loses more than 10% of birth weight, or who has not returned to birth weight by 3 weeks of age, needs a clinical assessment, a detailed feeding history, consideration of direct observation of feeding, and feeding support; any further investigations are reserved for findings on assessment. ^[1] Most infants recover birth weight by 14 days, intervention is usually not needed unless loss persists beyond 21 days, and up to 5% of breastfed babies lose more than 10%. ^[5]

Growth falters when the balance between energy in and energy out shifts against the child. The three mechanisms are inadequate caloric intake, inadequate absorption of nutrients, and increased energy requirement. ^{[4] [5]} The order of likelihood matters: inadequate intake is by far the most common, and within it are feeding problems, incorrect formula preparation, inadequate breast milk transfer, and disordered family feeding. ^{[4] [5]}

This group accounts for most faltering in both outpatient and inpatient series. ^{[4] [5]}

• Newborn and infant factors: low breast milk supply, poor latching, ineffective bottle feeding, incorrectly mixed formula, mechanical feeding difficulties such as cleft lip or palate, poor oral neuromotor coordination. ^{[4] [5]}
• Feeding behaviour and family feeding: disordered feeding, feeding aversion, distracted or chaotic mealtimes, prolonged grazing, inappropriate food choices, excessive low-nutrient drinks including fruit juice and flavoured sugar water that produce satiety before meals. ^{[4] [5]}
• Psychosocial and environmental: poverty, the strongest psychosocial risk factor, family stress, parental depression or anxiety (including postnatal depression), social isolation, poor parenting skills, limited access to food supplies or preparation facilities (water, electricity), unusual health beliefs, restricted diets. ^{[4] [5]}
• Eating disorders in older children and adolescents: avoidant/restrictive food intake disorder, pervasive refusal syndrome, anorexia and bulimia. ^[5]
• Gastrointestinal discomfort: gastro-oesophageal reflux, gastrointestinal pain, constipation, food allergy or intolerance. ^{[4] [5]}

One point from NICE deserves emphasis: neglect, family disadvantage and poor education were often assumed to be the cause in the past. Neglected children may be undernourished, but neglect is an uncommon explanation; significant associations with socioeconomic or educational factors have not been demonstrated. ^[2] Food insecurity is real, however, and up to 14% of US households experience it, sometimes first becoming apparent when growth faltering is diagnosed. ^[5]

• Gastrointestinal disease: coeliac disease, inflammatory bowel disease, milk protein allergy, chronic gastrointestinal infections including parasites and Helicobacter pylori, short bowel and chronic diarrhoea. ^{[4] [5]}
• Structural or congenital disease of the gut: biliary atresia, pyloric stenosis, tracheoesophageal fistula, pancreatic or hepatobiliary disorders. ^{[4] [5]}
• Inborn errors of metabolism. ^{[4] [5]}

• Chronic infections: HIV, tuberculosis, chronic respiratory infection. ^{[4] [5]}
• Cardiac, pulmonary and renal disease: congenital heart disease, chronic lung disease of prematurity such as bronchopulmonary dysplasia, renal disease. ^{[4] [5]}
• Endocrine and oncological: hyperthyroidism or thyroid disease, malignancy. ^{[4] [5]}
• Inflammatory conditions: asthma, inflammatory bowel disease, chronic inflammatory and rheumatological disease. ^[4]

Predisposing conditions include prematurity (under 37 weeks' gestation), low birth weight under 2500 g, congenital anomalies such as Down syndrome or cerebral palsy, developmental delay, poor dental health, tongue-tie in some settings, fetal growth restriction, and gastrointestinal disorders. ^{[4] [5]} Children with autism spectrum disorder have about four times the rate of gastrointestinal symptoms and are prone to behavioural feeding difficulties that raise the risk of malnutrition. ^[5]

Children with faltering growth are usually not in immediate danger, but certain combinations turn a benign problem into an urgent medical matter. ^{[1] [4] [5]}

• Rapid weight loss, severe undernutrition or a weight-for-age z score of minus 3 or lower. ^{[1] [5]}
• Symptoms or signs of an underlying disorder: protracted vomiting, bloody diarrhoea, chronic cough, fever, night sweats, dyspnoea, hepatomegaly or organomegaly, oedema, a heart murmur, developmental regression. ^{[1] [5]}
• New symptoms after the first assessment, which should trigger reconsideration of whether investigations are needed. ^[1]
• Safeguarding concerns: non-accidental injury, extreme parental impairment, poor parent-child interaction, failure to engage with care. ^{[1] [4]}
• Signs of dehydration, apathy, or a child who is acutely unwell. ^[4]
• Severe malnutrition without response to a well-delivered outpatient plan after several months. ^{[4] [5]}

A detailed feeding and social history is the single most effective investigation in faltering growth, and it costs nothing. ^{[1] [5]} It converts a vague label into a working understanding of what is happening on the plate. ^[4] Ask the person who actually feeds the child, and watch a feed if you can. ^[1]

NICE NG75 divides the feeding assessment by age and developmental stage. ^[1]

In milk-fed infants, consider whether these are contributing: ineffective suckling in breastfed infants; ineffective bottle feeding; feeding patterns or routines; the feeding environment; feeding aversion; parent-infant interaction and response to feeding cues; and physical disorders affecting feeding. ^[1]

In children taking solid food, consider mealtime arrangements and practices; types of food offered; food aversion and avoidance; parent-child interaction at mealtimes; appetite and interest in eating; and physical disorders affecting feeding. ^[1]

NICE suggests asking parents to keep a diary of food intake, types and amounts, together with mealtime issues such as settings and behaviour, to inform management and assess progress. ^[1] A standard breastfeeding assessment includes duration and frequency of feeds, milk supply and latching, while the formula history asks how the formula is stored, mixed and obtained. ^[5] For adolescents, a structured SSHADESS screen (strengths, school, home, activities, drugs, emotions or eating, sexuality, safety) can uncover disordered eating. ^[5] A brief developmental assessment, including validated autism screening at 18 months or older, is useful because developmental delay and autism are both risk factors and explanations for feeding difficulties. ^{[4] [5]}

The examination confirms the degree of undernutrition, looks for an underlying medical condition, checks development and observes the parent-child relationship. ^{[4] [5]} Weigh the infant or child unclothed, measure length accurately up to 2 years or height after 2 years, and in children over 2 years calculate the BMI centile. ^{[1] [5]} In children over 2 with concern about faltering growth or linear growth, BMI below the 2nd centile may reflect undernutrition or a small build, and below the 0.4th centile suggests probable undernutrition. ^[1] Plot all measurements on the appropriate chart and record them in the child's record. ^[1]

Important examination components include vital signs, muscle mass, fat deposition, hair and skin changes, hydration, dentition, and head circumference, which usually falls only late in severe malnutrition or suggests a genetic syndrome. ^[5] Mid-arm circumference, plotted on WHO or CDC charts, is an optional adjunct that assesses fat deposition, but it is not required for diagnosis. ^[5] Look for dysmorphology, organomegaly, heart murmur, respiratory compromise, anaemia, oedema, wasting and non-accidental injury. ^{[4] [5]}

Poor parent-child interaction, abnormal mental status and developmental delay are themselves important findings. ^[4]

Investigations should be guided by the history and examination; they are unlikely to reveal an underlying disorder in a child with faltering growth who is well and has no other clinical concerns. ^{[1] [5]} NICE recommends only considering urinary tract infection and, if the diet contains gluten, coeliac disease, and only performing them when indicated. ^[1] Routine extensive laboratory testing has little value in a well child with a normal history and examination. ^{[4] [5]}

When the picture suggests an organic cause, or initial treatment fails, these are the useful tests. ^{[4] [5]}

Do not admit for testing alone. NICE advises not admitting children with faltering growth unless they are acutely unwell or there is a specific indication such as starting tube feeding. ^[1]

The most important outcome is not the size of the number under the cursor, but the establishment of an agreed trend under an agreed team.

The aim of management is optimal growth velocity while supporting the family in the plan. ^{[4] [5]} Inadequate caloric intake is corrected first; the great majority improve with consistent outpatient attention. ^{[4] [5]}

If supply is poor or intake is the problem, support the mother to continue breastfeeding, advise expressing breast milk to protect supply, and give available breast milk before any infant formula. ^[1] Lactation consultation should be offered, although there is no high-quality evidence that behavioural interventions alone increase breast milk supply or infant weight. ^[5] Supplemental formula may increase weight, but often causes breastfeeding to stop. ^{[1] [5]} Human breast milk contains about 22 kcal per ounce and standard infant formulas deliver about 19 to 20 kcal per ounce when correctly mixed. ^[5]

Once the daily calorie deficit is estimated, more than routine standard formula concentration may be needed for catch-up. ^{[4] [5]} The following example recipe chart, adapted from a practical review, shows how concentrated mixes are produced; always check the manufacturer's own instructions because scoop sizes vary. ^[5]

Try first to correct the feeding so that energy density improves without mixing confusion: reviewing latch, frequency and milk transfer is often enough. ^[5]

Caregivers of toddlers and older children should be taught nutrient-rich foods in three meals and three snacks per day, with added sugars limited to 6 teaspoons, or 25 grams, daily. ^{[4] [5]} Appetite stimulants such as cyproheptadine are generally not recommended in straightforward faltering growth; they have limited roles in defined diseases such as cystic fibrosis and their benefit otherwise is unclear. ^{[4] [5]} Vitamin D is not a growth treatment, but vitamin D is recommended for breastfed infants to prevent rickets, and deficiencies such as iron and zinc, which are associated with malnutrition, should be treated. ^[5]

If growth does not respond to dietary advice alone, a short-term trial of dietary fortification with energy-dense foods, referral to a paediatric dietitian, and then a trial of an oral liquid nutritional supplement are the next steps. ^[1] Enteral tube feeding should be considered only when there are serious concerns about weight gain, an appropriate specialist multidisciplinary assessment of causes has been completed, and other interventions have been tried without improvement. ^[1]

Catch-up occurs when the child gains at roughly two to three times the average weight gain for age. ^[4] Published median daily weight gains are 26 to 31 grams from 0 to 3 months, 17 to 18 grams from 3 to 6 months, 12 to 13 grams from 6 to 9 months, 9 grams from 9 to 12 months and 7 to 9 grams thereafter, which can be used to set realistic parental expectations. ^[4] The correction of a caloric deficit usually improves growth faltering, and treatment is particularly important for neurodevelopment in the first 2 years, although the optimal pace of correction is not established. ^[5] Appetite stimulants and high-fat formulas have no clear advantage over standard formulas. ^[5] Vitamin D supplementation during pregnancy or early childhood has little effect on growth. ^[5]

Correct dental caries, sleep problems and chronic constipation; improve sleep and activity, and involve social work where there is food insecurity or family stress. ^{[4] [5]} Frequent follow-up is valuable, usually ranging from weekly to every few months depending on age and concern, and daily home weighing is discouraged. ^[4] Young infants need closer monitoring. ^[4] When measured, weight should be taken before feeding, on the same calibrated scale and at a consistent time. ^[4]

NICE sets out clear referral criteria. Discuss with or refer to an appropriate paediatric specialist service if any of the following are present: symptoms or signs that may indicate an underlying disorder; failure to respond to interventions delivered in primary care; slow linear growth or unexplained short stature; rapid weight loss or severe undernutrition; safeguarding concerns. ^[1]

Other useful thresholds and caveats come from the practical reviews. ^{[4] [5]} Hospitalisation is rarely needed, but should be considered when outpatient treatment fails after about 3 to 4 months, when there is severe comorbidity, failure to obtain reliable intake documentation, extreme family psychosocial risk, or severe malnutrition or dehydration. ^{[4] [5]} Inpatient structured feeding observation can document intake and support a faltering child, but weight gain in hospital does not by itself prove inadequate family care; consider weight gain above the 10th centile with normal weight gain on two evaluations at least one month apart as reassuring for successful treatment. ^[4] If severe, defined as a z score of minus 3 or lower, or refractory, adopt a multidisciplinary approach; tube feeding only after serious concerns, a multidisciplinary assessment of causes and failed less invasive measures. ^{[1] [5]}

Accelerated growth usually needs maintaining for 4 to 9 months to resolve faltering growth sustainably, so families should be prepared for a period of many weeks rather than a quick fix. ^[4]

• Faltering growth is a description of slow weight gain, not a diagnosis; identification depends on valid serial measurements and an agreed, centile-based threshold. ^{[1] [4]}
• NICE NG75 thresholds are a fall of 1 centile space if birth weight was below the 9th centile, 2 spaces if it was between the 9th and 91st, 3 spaces if above the 91st, and weight below the 2nd centile regardless of birth weight. ^[1]
• Monitor with WHO charts under 2 years and CDC charts from 2 years; z scores and BMI are now preferred to percentile definitions. ^{[3] [5]}
• Inadequate caloric intake is the commonest mechanism; gut disease, congenital problems and high metabolic demand are real but less common. ^{[4] [5]}
• Feeding history, social context and direct observation of feeding are more informative than blood tests in a well child. ^{[1] [5]}
• Milk-fed infants: watch ineffective suckling or bottle feeding, feeding patterns and environment, aversion, and cues. ^[1]
• Solid-fed children: consider mealtime arrangements, food offered, aversion or avoidance, and parent-child interaction. ^[1]
• NICE advises only considering urinary tract infection and, if gluten is eaten, coeliac disease; perform further investigations only if history and examination indicate. ^[1]
• Treatment is mostly outpatient: relaxed, calorie-dense feeding, family support, follow-up; catch-up runs at two to three times the average weight gain rate for age. ^[4]
• Hospitalisation is rarely necessary and is reserved for acute illness, extreme psychosocial risk or failed outpatient care; tube feeding is last. ^{[4] [5]}
• Faltering resolves over months, not days; recheck weight at agreed intervals and continue surveillance until a normal growth curve is re-established. ^[4]
• Neglect and social disadvantage are commonly assumed causes but are uncommon or unproven as sole explanations; food insecurity is real and should be addressed. ^{[2] [5]}
• Untreated early faltering can affect later height and cognition, which is why early, practical and kind management matters. ^[5]

• Dehydration and paediatric fluids
• Severe and moderate acute malnutrition
• Coeliac disease
• Prematurity and its complications
• Neonatal hypoglycaemia
• Infantile hypotonia and neuromuscular feeding problems
• Feeding disorders and aversion

NICE NG75 and WHO child growth guidance form the backbone of this topic; AAFP 2016 and 2023 reviews provided the tables on causes, history, feeding history, formula recipes and z-score classification. These are the editions used here. Any wording that describes doses, cut-offs or first-line care in this text comes from those sources, which are linked in the front matter.