Failure to thrive and poor weight gain
Also known as: Faltering growth, FTT, Poor growth
Failure to thrive, now more often called faltering growth, is a rate of weight gain in infancy or childhood that is lower than expected for age and sex. It includes poor weight gain, weight loss, and, in the more severe or prolonged form, reduced length or height and head growth. The same assessment covers unintentional weight loss in a child at any age.
Most cases are caused by inadequate energy intake relative to need. The most common contributing factors are feeding difficulty, food insecurity and psychosocial adversity. It can be the first sign of serious chronic disease (cardiac, renal, gastrointestinal, endocrine, metabolic, infectious, malignant) or of neglect.
Definitions.
- Faltering growth is a fall across one or more major centile lines (for example from the 50th to the 9th centile, or two centile spaces on the growth chart) for weight, or a weight under the 2nd centile (z score under minus 2) for age, or a weight for length under the 3rd centile.
- Poor weight gain is weight gain under the expected rate for age. Lower limits of normal in healthy children are under 20 g daily from 0 to 3 months, under 15 g daily from 3 to 6 months, under 10 g daily from 6 to 12 months, under 8 g daily from 1 to 2 years, and under 5 g daily from 2 to 5 years.
- Normal infants regain birth weight by 10 to 14 days, double it by 4 to 5 months, and triple it by 12 months. A weight loss of over 10% of birth weight after day 3, or failure to regain birth weight by 2 weeks, is abnormal.
- Moderate acute malnutrition is weight for length z score between minus 3 and minus 2 or mid upper arm circumference 115 to under 125 mm in children 6 to 59 months.
- Severe acute malnutrition is weight for length z score under minus 3, mid upper arm circumference under 115 mm, or bilateral pitting oedema (kwashiorkor).
- Stunting is height or length for age z score under minus 2 (chronic malnutrition), and underweight is weight for age z score under minus 2.
- Wasting is a low weight for length.
- Catch up growth is a rate of weight gain over the expected rate for age, needed to recover to the child's centile.
Classification by mechanism
- Inadequate intake (most common): insufficient breast milk transfer or poor latch, incorrect formula preparation or underfeeding, poor feeding technique, food insecurity, restricted diet (vegetarian or fad diets), feeding aversion, behavioural feeding disorder, sensory aversion, oral motor dysfunction, cleft palate, neurological impairment, prematurity, and neglect or deprivation.
- Inadequate absorption or loss: coeliac disease, cow's milk protein allergy, cystic fibrosis, pancreatic insufficiency, short bowel syndrome, chronic diarrhoea, giardiasis, inflammatory bowel disease, cholestatic liver disease, biliary atresia, protein losing enteropathy, lactose intolerance, and persistent vomiting (reflux, pyloric stenosis, obstruction).
- Increased energy requirement: congenital heart disease, chronic lung disease and bronchopulmonary dysplasia, cystic fibrosis, chronic infection (HIV, tuberculosis, recurrent urinary infection, parasitic infection), chronic inflammation (juvenile arthritis, inflammatory bowel disease), malignancy, hyperthyroidism, severe eczema, and burns.
- Metabolic and endocrine: hypothyroidism, growth hormone deficiency, adrenal insufficiency, diabetes mellitus (new onset, poorly controlled), diabetes insipidus, renal tubular acidosis, chronic kidney disease, rickets, inborn errors of metabolism, and Turner syndrome.
- Genetic and constitutional: familial short stature, constitutional delay of growth, small for gestational age without catch up, chromosomal disorders (Down syndrome, Turner syndrome), skeletal dysplasias, and Silver-Russell syndrome.
- Neurological and developmental: cerebral palsy, neuromuscular disease, autism spectrum disorder with restricted eating, hypotonia, and intellectual disability.
- Psychosocial and environmental: neglect, maternal depression, family conflict, poverty, abuse, parental mental illness, disordered attachment, and emotional deprivation.
- Eating disorders (older children and adolescents): anorexia nervosa, avoidant restrictive food intake disorder, and rumination.
- Weight loss in older children and adolescents: eating disorders, diabetes, hyperthyroidism, inflammatory bowel disease, coeliac disease, tuberculosis, HIV, malignancy (lymphoma, leukaemia), depression, anxiety, substance use, chronic infection, and Addison disease.
Epidemiology. Faltering growth affects 5% to 10% of children seen in primary care and about 3% to 5% of hospital admissions in young children. It is mostly due to inadequate intake in the absence of organic disease (80% or more of cases in high income settings).
- Globally, about 150 million children under 5 years are stunted and 45 million are wasted, with 13 million severely wasted. Undernutrition contributes to nearly half of child deaths.
- Severe acute malnutrition has a case fatality rate of 20% to 30% when untreated or badly managed, and under 5% with correct inpatient care.
- Common contributors in sub-Saharan Africa and South Asia include food insecurity, repeated diarrhoea and respiratory infection, HIV, tuberculosis, malaria, helminth infection, and poor complementary feeding practices.
- Coeliac disease affects about 1% of children, cystic fibrosis 1 in 2,500 births in people of European ancestry, and congenital heart disease 8 in each 1,000 births.
Mechanisms. Growth needs adequate energy and protein plus micronutrients, and is regulated by growth hormone, insulin-like growth factor 1, thyroid hormone, sex steroids and nutritional status. Growth fails when intake is inadequate (most common), absorption is reduced, losses are increased, energy needs are raised, or hormone action is impaired.
In infants, weight is affected first, then length, then head circumference with severe or prolonged undernutrition. Endocrine disease and genetic disorders typically slow height or length more than weight, whereas nutritional deprivation slows weight first.
Undernutrition impairs immunity, increasing infection, which further reduces intake and increases loss, causing a vicious circle.
Key distinctions.
- Weight falling across centiles with preserved length and head size suggests inadequate intake.
- Length and weight both falling with normal weight for length suggests constitutional or endocrine growth delay or genetic short stature.
- Weight falling after introduction of gluten or cow's milk suggests coeliac disease or allergy.
- Poor growth with recurrent chest infections, greasy stool and salty skin suggests cystic fibrosis.
- Poor growth with tachypnoea, sweating on feeding and hepatomegaly suggests heart failure.
- Poor growth with polyuria, polydipsia and acidosis suggests renal tubular acidosis, chronic kidney disease or diabetes.
- Weight loss with fever, night sweats and cough suggests tuberculosis.
- Weight loss with a distorted body image and food restriction in a teenager suggests anorexia nervosa.
- Poor growth with delayed milestones, hypotonia and coarse features suggests hypothyroidism or a genetic syndrome.
- Poor weight gain with a flat or fearful affect, poor hygiene and a history of unreliable feeding suggests neglect.
