Failure to thrive is a description applied to children whose current weight or rate of weight gain is significantly below that of other children of similar age and sex.

Infants or children that fail to thrive seem to be dramatically smaller or shorter than other children the same age. Teenagers may have short stature or appear to lack the usual changes that occur at puberty. However, there is a wide variation in normal growth and development.

In general, the rate of change in weight and height may be more important than the actual measurements.

It is important to determine whether failure to thrive results from medical problems or factors in the environment, such as abuse or neglect.

There are multiple medical causes of failure to thrive. These include:

• Chromosome abnormalities such as Down syndrome and Turner syndrome
• Defects in major organ systems
• Problems with the endocrine system, such as thyroid hormone deficiency, growth hormone deficiency, or other hormone deficiencies
• Damage to the brain or central nervous system, which may cause feeding difficulties in an infant
• Heart or lung problems, which can affect how oxygen and nutrients move through the body
• Anemia or other blood disorders
• Gastrointestinal problems that result in malabsorption or a lack of digestive enzymes
• Long-term gastroenteritis and gastroesophageal reflux (usually temporary)
• Cerebral palsy
• Long-term (chronic) infections
• Metabolic disorders
• Complications of pregnancy and low birth weight

Other factors that may lead to failure to thrive:

• Emotional deprivation as a result of parental withdrawal, rejection, or hostility
• Economic problems that affect nutrition, living conditions, and parental attitudes
• Exposure to infections, parasites, or toxins
• Poor eating habits, such as eating in front of the television and not having formal meal times

Many times the cause cannot be determined.

Infants or children who fail to thrive have a height, weight, and head circumference that do not match standard growth charts. The person's weight falls lower than 3rd percentile (as outlined in standard growth charts) or 20% below the ideal weight for their height. Growing may have slowed or stopped after a previously established growth curve.

The following are delayed or slow to develop:

• Physical skills such as rolling over, sitting, standing and walking
• Mental and social skills
• Secondary sexual characteristics (delayed in adolescents)

The doctor will perform a physical exam and check the person's height, weight, and body shape. A detailed history is taken, including prenatal, birth, neonatal, psychosocial, and family information. A Denver Developmental Screening Test reveals delayed development. A growth chart outlining all types of growth since birth is created.

The following laboratory tests may be performed:

• CBC (complete blood count)
• Electrolytes
• Urinalysis
• Thyroid function tests
• Other hormone studies
• Hemoglobin electrophoresis (to determine the presence of conditions such as sickle cell disease)
• X-rays to determine bone age