Nutritional Considerations in Failure to Thrive 

Failure to thrive (FTT) is both a descriptive term for various entities and a diagnosis. It is defined as a significant interruption in the expected rate of growth during early childhood. Because sequential measurements of growth are vital aspects of preventive pediatrics, failure to thrive is a concern for all pediatric heath care providers. All standard pediatric textbooks have sections on this topic,^[1] and numerous review articles have been written.^{[2, 3, 4, 5, 6]} However, despite significant attention, a meta-analysis of studies on industrialized children with this condition failed to demonstrate any significant adverse outcomes in this cohort.^[7] Still, failure to thrive can be a prelude to significant morbidity and mortality in the developing world, in impoverished children, and in children with various chronic illnesses.

Although specific anthropometric criteria to define failure to thrive vary, all describe children with inadequate or worsening growth over time. The most common definition is weight less than the third to fifth percentile for age on more than one occasion or weight measurements that fall 2 major percentile lines using the standard growth charts of the National Center for Health Statistics (NCHS).

Some authors have included height measurements as part of the definition; however, height measurements more precisely describe short stature. If weight parameters are significantly compromised, height can also be secondarily affected in individuals with failure to thrive. A European study examined a large cohort of children using various terms associated with pediatric growth compromise and documented a wide variance in the prevalence of this condition.^[8] Although serial measurements of head circumference are important in the evaluation of infants and toddlers, isolated failure of the head to grow should not suggest the typical failure to thrive differential.

In the developed world, the published literature indicates that although the differential diagnosis of failure to thrive is comprehensive, most children with this problem are diagnosed with predominantly psychosocial or nonorganic problems. However, because speech and feeding evaluations have become more commonplace and are more sophisticated, psychosocial compromise is now recognized as more likely to yield failure to thrive in those with subtle swallowing dysfunction or other organic conditions.^[9] As this fundamental paradigm is reconsidered,^{[10, 11]} the practicing child care provider must make every effort to identify simultaneous pathophysiology, regardless of how deprived the child with failure to thrive may appear.

Conversely, the contributions of dysfunctional familial dynamics, oppositional behavior, and depression to the failure to thrive noted in chronic illnesses must also be appreciated. Some authors have substituted a nonorganic failure to thrive paradigm for the organic failure to thrive paradigm, with individual children lying closer to one extreme or the other.^[12]

Normal growth and growth charts of term and premature infants, as well as the etiology, evaluation, management, and outcome of failure to thrive are discussed in this article. For information on energy malnutrition, see the eMedicine article Marasmus.

Although failure to thrive has historically been considered to be organic or nonorganic, a new view attempts to identify all contributing factors, often finding contributors from both categories in a single child. Nonorganic failure to thrive is almost always the result of inadequate energy intake. In addition to that problem, organic failure to thrive may also be the result of compromised use of ingested calories (usually vomiting or malabsorption and/or excessive losses [ie, protein-losing enteropathy]) and excessive metabolic demands. Prior to analyzing these entities, normal growth is reviewed.

Normal growth in term infants

The average birth weight for a term infant is 3.3 kg. Weight drops as much as 10% in the first few days of life, secondary to loss of excess fluid. By 10-14 days of life, birth weight should be regained. Breastfed infants who are fed smaller volumes of colostrum for the first few days regain birth weight a little later than bottle-fed infants.

On average, infants gain 1 kg/mo for the first 3 months, 0.5 kg/mo from age 3-6 months, 0.33 kg/mo from age 6-9 months, and 0.25 kg/mo from age 9-12 months. Term infants double their birth weight by age 4-6 months and triple their weight by age 12 months. An alternative schema to use is that term infants gain almost 30 g (1 oz) per day for 3 months and then almost 15 g (0.5 oz) per day for the next 6 months. From age 9 months until the child is a toddler, the average weight gain is roughly 0.25 kg/mo (or 0.5 lb/mo). Afterwards, the weight gain is about 2 kg/y through early school age.

Caloric intake to assure adequate intake in a normal infant is 100-110 kcal/kg/d for the first half year and 100 kcal/kg/d for the second half of the first year. Beyond 10 kg, 50 kcal/kg/d is required until 20 kg. Beyond 20 kg, 20 kcal/kg/d are necessary.

Term infants grow 25 cm in length during the first year, 12.5 cm in the second year, and then slow down to approximately 5-6 cm between age 4 years and the onset of puberty, at which time, growth can increase up to 12 cm per year.

The average head circumference is 35 cm at birth and rapidly increases to 47 cm by age 1 year. The rate of growth then slows, reaching an average of 55 cm by age 6 years.

Also, the upper-to-lower body segment ratio changes with growth. Normally, the ratio at birth is 1.7, the ratio at age 3 years is 1.3, and the ratio by age 7 years becomes 1. The lower body segment is measured from the symphysis pubis to the floor.

Normal growth in premature infants

When plotting growth charts for premature babies, a "corrected age" should be used. This corrected age can be calculated by subtracting the number of weeks of prematurity from the postnatal age. Special growth charts based on gestational age rather than chronological age have been developed for infants, beginning at 26 weeks' gestational age. However, because these charts represent a compilation of a relatively small number of infants, they may not be completely reliable. Whichever technique is used for premature babies (eg, adjustment of age, using specific premature growth charts), consistency of methodology is essential. Once a method for plotting growth is chosen, that technique should be followed each time plotting occurs. Prior to 40 weeks' gestation, some infants may require as much as 120 kcal/kg/d to ensure adequate weight gain.

Catch-up growth is attained at approximately age 18 months for head circumference, age 24 months for weight, and age 40 months for height. Subsequently, normal growth charts can be used. In some premature babies with very low birth-weight, catch-up growth does not occur until early school age.

Growth charts

Growth charts were developed by the NCHS based on data collected through the Third National Health and Nutrition Examination Survey III. They have been used since 1977 and are available for males and females aged 0-36 months and aged 2-18 years. The growth charts for boys and girls aged 0-36 months include weight and height for age and head circumference; growth charts for both age groups include weight for stature.

These charts have been revised and are available from the Centers for Disease Control and Prevention (2000 CDC Growth Charts: United States).^[13] The new charts are applicable to infants, children, and adolescents from birth to age 20 years and have 7 percentile curves (5th, 10th, 25th, 50th, 75th, 90th, 95th). Charts are available for use in subspecialty patients (eg, endocrine, gastroenterology), with additional third and 97th percentile curves. Body mass index (BMI) charts, which are available for individuals aged 2-20 years, have replaced the weight-for-stature charts. BMI is calculated by dividing weight in kilograms by height in meters squared.

Accurate measurements are essential to the interpretation of growth charts. Scales need to be regularly calibrated; length should be carefully measured, and head circumference should be measured using standardized techniques.

Alternate growth charts are available for children who are breast fed and for children with Down syndrome,^[14]Turner syndrome,^[15] achondroplasia,^[16] meningomyelocele, low birth weight, and very low birth weight. No matter which growth chart is used, the most valuable information is obtained by careful measuring and plotting on the same chart over time. Infants and children should remain within 1-2 percentile curves over time.

Frequency

United States

In reports from 1980-1989, failure to thrive accounted for 1-5% of tertiary hospital admissions for infants younger than 1 year. As many as 10% of children in primary care settings show signs of failure to thrive. The incidence is highest in children with prematurity and with other medical conditions. The proportion of nonorganic failure to thrive among all infants with failure to thrive is much higher in the United States and other industrialized countries than in the developing nation.

International

In underdeveloped countries, malnutrition manifesting as failure to thrive is more common.

Mortality/Morbidity

Ultimate physical growth and cognitive development may be decreased in children with long standing failure to thrive, especially with an early onset. However, efforts to analyze the published data have not yielded unequivocal confirmation in children in the developing world.^[7] Earlier publications have described more cognitive deficits in nonorganic than organic failure to thrive.^[17]

In developing countries, malnutrition is a significant cause of mortality, whether directly or secondary to complications (eg, infection). Among children with certain illnesses, failure to thrive is an independent risk factor for premature mortality, such as with HIV infection^[18] and epidermolysis bullosa.^[19]

Race

Failure to thrive can occur in all socioeconomic strata, although it is more frequent in families living in poverty. Studies indicate increased incidence in children receiving Medicaid, children living in rural areas, and children who are homeless.

Sex

Nonorganic failure to thrive is reported more commonly in females than in males.

Age

The term is mainly reserved for growth compromise in young children.