Calories from food provide energy for the body’s maintenance functions of repair, regulation, metabolic functions, replacement of losses, and daily activity. Children have additional caloric requirements because they must also grow. Children under the age of 3 years whose caloric needs are not met do not grow according to published norms and are said to have failure to thrive (FTT) or growth faltering. FTT raises serious concerns. It is important to have a systematic, stepwise approach to the diagnosis and management of poor growth in young children and to follow growth over time.
The term failure to thrive is used to describe growth failure that accompanies many pathologic conditions as well as psychosocial causes. Differentiation between organic (biomedical) and nonorganic (psychosocial/environmental) is not always useful; children often have a combination of psychosocial and biomedical problems. Children with medical conditions will often have psychosocial issues related to eating and dysfunctional feeding patterns with caregivers. Children with primarily social or emotional issues around eating may develop medical consequences of undernutrition.
(See Nelson Textbook of Pediatrics, p. 250.)
There is a poor yield from exhaustive laboratory evaluations of most children with FTT. Testing should be based on clues from the history and physical examination. Children with biomedical and/or psychosocial causes of FTT may or may not gain weight in institutional settings, and this short-term outcome is not always diagnostic.
The best diagnostic tool available to the clinician is a comprehensive history, including diet, family, growth (over time) and social histories, and a complete review of systems; and a complete physical examination. Further work-up should be directed by results from this initial evaluation.
Normal Growth
Newborns typically lose up to 10-12% of their birthweight during the first few days of life and regain this weight by the age of 2 weeks. Subsequently, they gain weight at a steady pace of about 1 oz per day for the first 3 months; gain at half to two thirds that rate for the next 3 months and half to two thirds again for the next 6 months. This results in a doubling of birthweight by the age of 4-6 months and a tripling before 1 year. Height and head circumference grow at similar well-defined rates. These three growth parameters should be plotted on appropriate growth charts and monitored for adherence to standard growth rates. Children grow in a stepwise manner, but on average their growth pattern follows the accepted curves (see Chapter 43 ). Online tools are available to assist with the determination of growth status ( peditools.org ).
Between the ages of 1 and 3 years, if caloric intake is normal, the child’s growth adjusts to his/her genetic potential. Ultimate height is determined by additional factors, among them rates of bone maturity and pubertal development (see Chapter 43 ). Considerable energy from ingested food is required to achieve this growth. The energy balance can be described by the following equation, in which E equals energy:
E IN = E OUT + E growth + E stored
E OUT is the sum of basal metabolic rate, energy expended in physical activity, and the energy needed for food digestion. Children should be in a positive energy balance for growth. Any imbalance in this energy equation (losing or using more calories than are ingested) results in abnormal growth patterns. Weight is usually affected first, followed by height and finally head circumference if the energy imbalance is severe and prolonged in young children.
Definitions
FTT is a sign, not a diagnosis. FTT is generally used to describe children younger than 2 or 3 years who meet any of the following criteria:
- 1.
Growth under the third percentile on World Health Organization (WHO) weight for age growth charts (<3% = less than 3 standard deviations below mean)
- 2.
Weight for height or body mass index (BMI) less than the 5th percentile
- 3.
Growth patterns that have crossed two major percentiles downward on the weight for age charts within 6 months
- 4.
Growth velocity less than normal for age
There are inherent problems with these definitions. Three percent of the population is at or below the 3rd percentile, and so those who are growing appropriately per their genetic potential must be differentiated from those with growth problems. The child who has been obese and is now approaching normal weight for height, crossing major weight percentiles in the process should not be considered a child with FTT. Some children are naturally slim. The clinician must exercise considerable judgment before raising the concern of poor growth.
Additional terms are used to describe children who are not growing well. A child has wasting if the weight for length or weight for height is below –2 standard deviations (or −2 z-scores which is equal to <3 centile). Stunting is defined as a child whose height or length is less than −2 z-scores due to chronic undernutrition. In the third year of life, children are described as underweight if weight/age is <5% or if BMI is <5% or 10%. Short stature or microcephaly alone is not due to nutritional deficiencies ( Table 9.1 ).
| Weight | Height | Head Circumference | Associated Diseases | |
|---|---|---|---|---|
| Type I | Decreased | Decreased/normal | Normal | Malnutrition of organic or nonorganic etiology, usually secondary to intestinal, pancreatic, liver diseases or systemic illness or psychosocial factors |
| Type II | Decreased | Decreased | Normal | Endocrinopathies, bony dystrophy, constitutional short stature |
| Type III | Decreased | Decreased | Decreased | Chromosomal, metabolic disease, intrauterine and perinatal insults, severe malnutrition |
Interpretation of Growth Charts
The evaluation for any child who is not growing well includes a careful analysis of growth charts. A review of the growth pattern over time is the most useful. Measurements of length are the most susceptible to error; standard procedures should be used (see Chapter 43 ). Possible errors in weight, head circumference, date of birth, or plotting on the growth chart should all be considered. Once the correct data are available, the charts should be examined to answer the following questions:
- •
Are the measurements of length and weight proportionate?
- •
Has the head grown proportionately?
- •
How severe are the deficits of each measurement, relative to what is expected?
- •
When did the problem start and progress?
- •
Is the problem acute or chronic?
- •
What environmental factors were present at the start of this process (weaning, introduction of new foods)?
Although weight is usually the most readily available measurement, measurement of length is particularly critical, because it serves as the point of reference for other diagnostic considerations. The best way to obtain accurate length measurements is to use a specially calibrated length board with a fixed headpiece and a movable footpiece. In the absence of such a device, the examiner can use a table or desk with the infant’s head pressed against the wall and a firm square box or thick textbook for the sliding footer. Measurements obtained with the infant lying on a mattress and marked with a pen on the sheet are not accurate (see Chapter 43 ).
The choice of growth curves is important. In the United States, the recommendation is to use the WHO charts from birth through the second year of life ( http://www.cdc.gov/growthcharts/who_charts.htm ) (see Chapter 43 ). Some children previously classified as FTT now fall into the normal range. Their health status may be worse than those classified as within normal range on both charts. The 2000 age- and gender-specific National Center for Health Statistics growth charts published by the Centers for Disease Control and Prevention combined data across geographic and ethnic populations and are appropriate to use for children over 24 months of age.
Conventions differ in whether to plot age in relation to actual birth date or to use corrected gestational age. Growth charts following children prenatally to infancy are available (see Fenton and Olsen at peditools.org ). Beyond the equivalent of 40 weeks of gestation, standard charts can be used, keeping in mind that premature infants may not catch up on all parameters for 2 or 3 years.
Because infants with FTT no longer follow their growth curves, the usual convention of expressing growth measurements in relation to normal percentiles is not always useful. Researchers use weight/length or BMI z-scores to better define and assess degree of malnutrition ( Table 9.2 ).
| BMI z-Score | Weight for Length Percentile | Weight Deficit (for Current Length) | Degree/Risk of Malnutrition |
|---|---|---|---|
| 0 | 50% | 90–100% | Normal |
| −1 | 2.4–15.9% | 80–90% | Mild |
| −2 | 0.2–2.3% | 70–80% | Moderate |
| −3 | <0.2% | <70% | Severe |
Some conventions classify the severity of wasting or “malnutrition” by the weight deficit for the current length. Loss of about 40% of expected weight for length (actual weight divided by expected weight for length <60%) is the extreme of wasting that is compatible with survival. Therefore, 80-90% actual weight divided by expected weight for length corresponds to mild, 70-80% is moderate, and 60-70% is severe. These calculations are critical for planning nutritional rehabilitation and therefore essential to the overall diagnostic and treatment processes.
It is important to note the following points:
- 1.
Infants and toddlers who are short in proportion to weight should be considered to have primary growth problems, including various endocrine and skeletal disorders (see Chapter 43 ) (see Table 9.1 ).
- 2.
Infants who have had inadequate caloric intake will be abnormally thin. If the problem developed at some time after birth, weight will drop off before changes in length or head circumference.
- 3.
Infants with disproportionately small heads may have primary neurologic problems affecting brain growth because head growth is the last to be affected by malnutrition and is not characteristic of primary skeletal growth problems (see Table 9.1 ). An alternative diagnosis is craniosynostosis, or early closure of skull growth plates.
Several examples of how these patterns may be interpreted are presented in Figs. 9.1 to 9.4 . Growth charts adjusted for abnormal head size (micro- or macrocephaly) are not available. This factor becomes of relatively less importance as the child ages, but during infancy may significantly affect the weight percentile and requires clinical judgment to assess.
Disease-specific growth charts have been developed for certain populations (e.g., trisomy 21, skeletal dysplasias). Their use is most appropriate for conditions that affect muscle and bone development (e.g., Russell-Silver syndrome). Any other disease -specific charts should be used in conjunction with the WHO charts.
Epidemiology
FTT is found in all populations, but has a higher prevalence among children of low socioeconomic status compared to those in higher socioeconomic groups. FTT accounts for up to 5% of all hospitalizations; up to 10% of children may have FTT at some point in time. Most affected children with nutritional problems present before the age of 3 years.
Clinical Presentation
Parents often voice concerns about their young child’s weight gain. They may complain that their child is a picky eater or seems not to drink enough formula, or they worry that breast milk supply is inadequate. Very commonly, parents complain that their child is not as big as a similar-aged child or a sibling at that age. Many such children are growing normally. Plotting the child’s growth and reviewing it with the parent is usually reassuring, or it may serve to confirm the parents’ concerns. When families raise concerns about growth, regardless of whether a problem exists, the child and the weight have already become a focus of concern for that family. Often parents have already put a great deal of effort into changing the child’s eating patterns. The child’s real or perceived weight or appetite problem may cause intrafamily conflict. In this setting, conversations about the child’s growth may carry a high emotional charge.
However, it is often the physician who is first to raise concerns. These suspicions can be confirmed by carefully plotting the growth parameters. The clinician must then prioritize the clinical issues and decide whether the FTT should be addressed immediately or deferred for evaluation and management at another time in the very near future. In rare cases, the growth failure is so severe (child is <60% of ideal body weight for height) that immediate hospitalization must be instituted to begin nutritional rehabilitation. In this case, the evaluation can take place over several days, while therapeutic nutritional interventions are ongoing.
Approach to Determining Etiology
Clinicians need to have a broad approach to determining etiology of FTT for each child. Many children with FTT, particularly those with chronic diseases, have a mixed pattern of increased needs or losses attributable to organic causes, along with environmental causes leading to calorie deprivation.
There are several growth conditions that result in smaller than normal size but that are not due to calorie insufficiency. Children with constitutional delay usually grow normally over the first year, but weight and height decelerate to near or below the 5th percentile followed by growth at normal rates along their new curve (see Chapter 43 ). The symmetric deceleration of height and weight is a clue that the child does not have calorie insufficiency. Infants who are born small for gestational age and are symmetrically small are believed to have a reduced number of somatic cells in relation to their normal-sized peers as a result of an early intrauterine event. Infants who are asymmetrically small for gestational age, with sparing of the head circumference and possibly length, suffered a late intrauterine event, such as poor maternal nutrition or placental insufficiency. These infants often eat voraciously and experience catch-up growth early in life. Children with genetic short stature have short height for age with appropriate low weight.
Children with FTT caused by calorie insufficiency typically have decreased weight gain, at first with sparing of height and head circumference (wasting). Long-standing calorie insufficiency results in height deceleration (stunting). Height or length is the best predictor of chronic malnutrition. Only in the worst, long-standing cases is head growth decreased. This typical pattern suggests calorie insufficiency and informs the clinician of the chronicity of the problem.
There are several approaches to the differential diagnosis. The functional approach determines whether there is a problem with increased calorie requirement or utilization, inadequate calorie intake, or increased calorie loss ( Table 9.3 ). The systems approach focuses on the identification of the organ system or systems that might be responsible for the poor growth. A careful history can point the clinician toward a particular system to consider for further diagnostic evaluation ( Table 9.4 ).
| Excessive Calorie Needs |
|
| Inadequate Calorie Intake |
|
| Increased Calorie Loss/Failure to Incorporate Ingested Calories |
|
| Psychosocial/Behavioral |
|
| Neurologic |
|
| Renal |
|
| Endocrine |
|
| Genetic/Metabolic/Congenital |
|
| Gastrointestinal |
|
| Cardiac |
| Cyanotic heart lesions Congestive heart failure |
| Pulmonary/Respiratory |
|
| Miscellaneous |
|
| Infections |
|
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