Newborn infants should regain their birth weight by two weeks of age; any child who has not may be categorized as failing to thrive.

Newborns may fail to regain their birth weight if there is inadequate caloric intake from inefficient breastfeeding or from improper preparation (i.e. dilution) or inadequate intake of formula. Inadequate caloric intake may also be secondary to a) severe gastroesophageal reflux disease or b) central nervous system disease leading to poor muscle tone and subsequent poor feeding (e.g. as seen in Down Syndrome)

Severe milk protein allergy or cystic fibrosis may contribute to malabsorption. Infection results in inadequate calories for growth, as the calories instead go to fighting infection. Congenital heart disease (inefficient heart) results in excessive caloric requirement.

Older Infants

Around 6-9 months of age, there is a natural growth deceleration. This correlates with the introduction of solid food and gradual decrease in the total amount of formula or breast milk ingestion. Deceleration is most noticeable when weight percentiles have previously exceeded height percentiles. These children may be following normal growth variance and not failing to thrive.

This deceleration may be more pronounced in three groups:

Children who have poor weight gain secondary to inadequate nutrition intake will typically begin to cross percentiles in weight before height. Malnutrition tends to "spare the brain" as much as possible so that large decrements in percentile for head circumference are unusual and found only in cases of prolonged or severe malnutrition.

Beyond the newborn period, into infancy, several other disease processes may manifest as failure to thrive.


After one year of age, solid foods constitute the majority of the child's diet, and formula should be replaced by whole milk. Toddlers may continue to breastfeed beyond one year of age, but solid foods should comprise the majority of their diet. Many children will have a natural decrease in appetite because of slower growth after the first year. If parents are unaware of this expected decrease in appetite, they may respond by offering frequent snacks or large quantities of juice which is generally high in sugar but low in nutritional value. The sugar may fill the child (i.e. not hungry for other foods), which then contributes to inadequate total caloric intake.

More Information

Additional information about juice intake is available from the American Academy of Pediatrics policy statement on Lipid Screening and Cardiovascular Health in Childhood. Table 5-1, or from the policy statement of the AAP on juice intake  



Underlying chronic inflammatory, malignant or metabolic conditions may still be contributors to failure to thrive at this age as well as the previously mentioned causes of malabsorption and

Other contributors

Psychosocial issues must be considered during a work-up for failure to thrive. If no organic cause can be found, failure to thrive may be rooted in poverty, family dysfunction, poor parenting skills which contribute to inadequate caloric intake, and/or complex interactions involving stress responses even in the presence of adequate calories. In some situations, the child may fail to thrive until removed from the non-nurturing environment. In many cases the etiology is complex (i.e. organic and non-organic) and solutions are not simple.

Economic stress may tempt a parent to dilute formula to make it last as longer. Thankfully, with the advent of nutritional support programs in the United States (e.g. WIC), this is less of a problem than it once was. However, whenever evaluating a child for failure to thrive, a complete history should include formula preparation technique and a thorough dietary history.