What Is Failure to Thrive?

There is a lack of consensus about the definition of failure to thrive (FTT), a term that has been in use for many years. Most broadly, it is used to describe a patient of any age with poor weight gain, particularly after a stable growth pattern has been previously established. FTT has also been used on occasion to describe poor linear growth in children, or a slow increase in both weight and height/length. Although agreement exists that FTT must be defined by anthropometric indicators, a dizzying variety of anthropometric criteria have been used for this purpose, some of which are listed in Table 12-1 . Multiple cut-off values for FTT have been proposed for weight-for-age, height-for-age, weight-for-height, weight as percentage of median weight for age and/or height, and height as percentage of median for age. Other criteria are based on growth velocity, such as downward crossing of at least two major percentile lines, weight gain z-score below the 5th percentile, and weight gain less than a given number of grams per day. Conditional growth measures, such as conditional gain z-scores, which evaluate weight gain relative to gender and birth weight, have also been recommended. Some experts advocate the use of skin-fold thickness measurements. The lack of consensus on a definition of FTT has been frequently noted, and as pointed out by Wilcox et al., may well be unavoidable given the inability of any one growth index to apply to all situations. Because of the variable definition of FTT, the prevalence is difficult to quantify. Another factor that makes prevalence data difficult to interpret is the inconsistent inclusion of infants with low birth weight in published studies.

For purposes of this chapter, the term “failure to thrive” will be used to mean poor weight gain in children younger than 2 years of age, regardless of cause. This syndrome of malnutrition is brought on by a combination of organic, behavioral, and environmental factors. Of interest, in the United States, diagnosis of a patient with “failure to thrive” as opposed to “malnutrition” may have negative consequences for reimbursement. FTT has also garnered attention as a politically insensitive term, although it is still commonly used by practitioners. “Malnutrition” is a term that presents similar challenges in definition, and is a condition that cannot be easily described solely by anthropometry. Ideally, malnutrition is assessed via a Subjective Global Nutritional Assessment, although this evaluation will require more time and more application of professional judgment than does anthropometry alone. However, for purposes of practicality, one can use Table 12-2 for translation of growth percent standards into categories of severity of chronic malnutrition, with use of the Waterlow technique as published by the American Academy of Pediatrics (AAP). Other relevant terms include wasting , or low weight for height, suggestive of more acute malnutrition, and stunting , or decreased height for age, which is suggestive of chronic undernutrition. Kwashiorkor is protein-energy malnutrition, the result of protein deficiency relatively greater than caloric deficiency. Marasmus is severe malnutrition secondary to inadequate total caloric intake.

Diagnosing Failure to Thrive

Regardless of the anthropometric definition chosen by a practitioner, clinic, or institution, the diagnosis of FTT is predicated on accurate measurements of weight and length, or height. It is preferable to obtain serial measurements on the same scale, to avoid equipment-related variability, and to have the same provider obtain serial measurements of length/height. Length/height is more difficult than weight to measure accurately, as it can be easily confounded by squirming, posture, nonstandardized techniques, and inconsistently trained personnel. One center found that on standardized re-measurement of infant length, “true” length was an average of 2.23 cm different from hospital admission length. It is recommended that infant length be measured with the infant wearing a diaper or light underclothing only, using a calibrated board with fixed headpiece and movable footpiece. Starting at the age of 24 months, children who can stand unsupported should be measured on a stadiometer.

The growth charts used for reference, published by World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC), are derived from measurements of healthy, breast-fed children. The WHO charts, most recently released in 2006, are based on data from the Multicenter Growth Reference Study and reflect measurements of breast-fed children of nonsmoking mothers from higher social classes in Brazil, Ghana, Oman, and India, and also from Norway and the United States. The WHO charts are intended to describe the growth of healthy children under optimal conditions. The CDC charts, on the other hand, are a “growth reference” rather than a standard. The CDC charts, released most recently in 2000, replaced the 1977 National Center for Health Statistics (NCHS) growth charts. They describe the growth of children in the United States during a span of approximately 30 years (1963-1994), using data from multiple studies. The CDC recommends using modified versions of the WHO curves for children younger than 24 months. These modified curves include the 2.3rd and 97.7th percentiles and are available at http://www.cdc.gov/growthcharts . However, for children older than the age of 24 months, the CDC growth charts are recommended, at least in part because they extend all the way through adolescence. The weight of children born preterm should be corrected for gestational age until they have reached 24 months of postnatal age, and length should be corrected until 40 months of postnatal age.

Pitfalls in Diagnosing Failure to Thrive

Children who meet anthropometric criteria for FTT may in fact be healthy and normally developing. Prior to making a diagnosis of FTT and initiating a medical workup, the medical professional should consider whether a child’s slow weight gain may be constitutional and similar to that of siblings or other family members—in other words, a value that is 2 standard deviations (SD) below the mean may be normal given a particular child’s genetic potential. Statistically speaking, 2.5% of healthy children would be expected to fall below this value on the WHO growth curves.

Although some normal infants may have low weight or slow growth from the start, it is also possible for normal, healthy infants to experience “catch-down” growth. This phenomenon occurs when a child who may have been born large for gestational age or who had very rapid early weight gain then experiences a deceleration in weight gain, ultimately arriving at his or her “correct” weight. A review of data gathered in the 1960s from the Child Health and Development Study (CHDS) showed that from birth to age 5 years, approximately 6% of children experienced downward crossing of at least 2 major percentile lines for weight-for-age. The data excluded patients seen for sick visits as well as those born with intrauterine growth retardation (IUGR), serious congenital anomalies, or as multiple births. For these reasons, a period of “watchful waiting” for other signs of illness may be prudent before making a diagnosis of or beginning an evaluation for FTT in a well-appearing child who had a normal birth weight. For infants with IUGR, the first 6 months postnatally comprise the period for maximal catch-up growth, so that evaluation of growth faltering during this sensitive interval is particularly important.

In the past, FTT was thought to be strongly related to neglect, poverty, and emotional detachment by the mother, or “maternal deprivation syndrome.” These findings have since been challenged, at least for populations in the United States and the United Kingdom. The term “growth faltering” may be preferred, as it avoids the pejorative use of the term “failure,” which to many feels judgmental of the child and his or her family. When parents see that their child is not growing well, they often already experience anxiety and self-blame in addition to their concerns about the child’s health. A blaming attitude on the part of the clinical team, which leads to anger or increased guilty feelings on the part of the primary caregivers, can be disruptive to the therapeutic relationship with the family, and could even interfere with the family’s ability to nurture the child. In other words, the pediatrician “must be an advocate for the child without becoming an adversary of the parents. In many cases the pediatrician must also become an advocate for the child’s family.”

Pitfalls in Diagnosing Failure to Thrive

Children who meet anthropometric criteria for FTT may in fact be healthy and normally developing. Prior to making a diagnosis of FTT and initiating a medical workup, the medical professional should consider whether a child’s slow weight gain may be constitutional and similar to that of siblings or other family members—in other words, a value that is 2 standard deviations (SD) below the mean may be normal given a particular child’s genetic potential. Statistically speaking, 2.5% of healthy children would be expected to fall below this value on the WHO growth curves.

Although some normal infants may have low weight or slow growth from the start, it is also possible for normal, healthy infants to experience “catch-down” growth. This phenomenon occurs when a child who may have been born large for gestational age or who had very rapid early weight gain then experiences a deceleration in weight gain, ultimately arriving at his or her “correct” weight. A review of data gathered in the 1960s from the Child Health and Development Study (CHDS) showed that from birth to age 5 years, approximately 6% of children experienced downward crossing of at least 2 major percentile lines for weight-for-age. The data excluded patients seen for sick visits as well as those born with intrauterine growth retardation (IUGR), serious congenital anomalies, or as multiple births. For these reasons, a period of “watchful waiting” for other signs of illness may be prudent before making a diagnosis of or beginning an evaluation for FTT in a well-appearing child who had a normal birth weight. For infants with IUGR, the first 6 months postnatally comprise the period for maximal catch-up growth, so that evaluation of growth faltering during this sensitive interval is particularly important.

In the past, FTT was thought to be strongly related to neglect, poverty, and emotional detachment by the mother, or “maternal deprivation syndrome.” These findings have since been challenged, at least for populations in the United States and the United Kingdom. The term “growth faltering” may be preferred, as it avoids the pejorative use of the term “failure,” which to many feels judgmental of the child and his or her family. When parents see that their child is not growing well, they often already experience anxiety and self-blame in addition to their concerns about the child’s health. A blaming attitude on the part of the clinical team, which leads to anger or increased guilty feelings on the part of the primary caregivers, can be disruptive to the therapeutic relationship with the family, and could even interfere with the family’s ability to nurture the child. In other words, the pediatrician “must be an advocate for the child without becoming an adversary of the parents. In many cases the pediatrician must also become an advocate for the child’s family.”

Why Is It Important to Identify Patients With FTT?

As noted earlier, FTT is not itself a disease, but rather a sign of an underlying problem, whether that problem is rooted in medical illness, behavioral or psychosocial difficulties, or a combination of all. The identification and treatment of FTT is intended to avoid long-term sequelae of micronutrient deficiencies, developmental delay, and suboptimal linear growth.

Infants with FTT have long been thought to be at risk of lower cognitive performance. When smaller studies (n < 225) are pooled, these children have been found to have a mean decrease of 3 IQ (intelligence quotient) points compared to controls. These findings have been confirmed in a large prospective cohort. An analysis of 14,775 children in the Avon Longitudinal Study of Parents and Children (ALSPAC) demonstrated that children whose weight faltered before the age of 9 months had a lower total IQ, by 2.7 points on average, at age 8 years. However, these children did not have poorer outcomes in psychosocial development, such as attention, social communication, and self-esteem. Neither did they have poorer outcomes in educational attainment after correcting for factors such as socioeconomic status. However, as the authors of one of the ALSPAC papers point out, their study was done “in a resource-rich society with a good education system.” Outcomes may be different in developing countries. In addition, in the special population of extremely preterm infants, those in the lowest quartile of weight gain in early life had a significantly higher risk of cerebral palsy and neurodevelopmental impairment than did those in the highest quartile. Furthermore, enhanced early nutrition has been shown to have neurocognitive benefits in this particular population of infants with FTT.

Micronutrient deficiencies can also contribute to poorer outcome in children with poor dietary intake and FTT. Early iron deficiency is well known to cause irreversible developmental deficits that carry into adulthood, including decreased likelihood of completing secondary school or marrying, and an increased likelihood of poor emotional health.

Linear growth is also decreased among children who had FTT in infancy. In one study, a height difference of 5.4 cm at age 8 years was noted between children of normal birth weight, who developed FTT in infancy, and normal controls. In the ALSPAC cohort, children with early growth faltering were within population norms for height and weight at age 13, but were still significantly smaller than children in the control group.

Causes and Evaluation of FTT

Failure to thrive is often categorized as “organic,” meaning that a child’s poor growth is caused by an underlying diagnosable medical condition, versus “nonorganic,” or secondary to inadequate caloric intake for a variety of psychosocial causes. This distinction is often inadequate because FTT may often be multifactorial, and in the case of any one child, both “organic” and “nonorganic” factors may come into play.

The differential diagnosis for FTT is extremely broad. Almost any severe or chronic childhood illness may cause poor growth, whether directly or indirectly. Factors include inadequate nutritional intake, inadequate absorption, or increased metabolic needs. Even children who may be at risk for obesity later in life, such as those with Prader-Willi syndrome, may have poor weight gain in infancy and require special nutritional attention to achieve appropriate early growth. However, more than 80% of children with inadequate growth do not have any underlying medical disorder.

The evaluation of FTT, therefore, requires a careful history to elicit any symptoms suggestive of inadequate intake (e.g., poor suck or swallow), feeding aversion, malabsorption (e.g., diarrhea), or increased metabolic demand (e.g., sweating with feeds, as may be seen in congenital cardiac disease). History taking should include family growth patterns and medical conditions as well as the mother’s intrapartum health and weight gain, alcohol or other substance use, symptoms of subclinical or “TORCH” infections, and risk of toxic occupational or environmental exposures such as lead. Birth history, including gestational age, birth weight, and any antenatal concern, is also of great importance in interpreting a child’s growth trajectory. Additional information that is essential in reaching an appropriate diagnosis can be obtained with a thorough discussion of feeding behaviors and cir­cumstances, as outlined in the AAP’s Pediatric Nutrition Handbook and presented with some modifications in Box 12-1 .

Participation of a social worker may be helpful in exploring some of the issues relevant to the child’s health and nutritional environment. In addition, involvement of a lactation consultant, occupational or speech therapist, and a variety of medical specialists may be necessary to properly address common maternal and infant factors in early breast-feeding that can lead to inadequate milk production and/or poor latch, and for coordination of breathe-suck-swallow patterns in term or preterm infants with oral motor delay. Consultations with ear, nose, and throat (ENT) specialists and/or neurologists, in particular, are often indicated when an infant is unable to suckle effectively and there is concern for oropharyngeal dysphagia.

A detailed physical examination is essential for the evaluation of FTT, with the goals of identification of chronic illness or neglect/abuse, recognition of growth-altering syndromes, and documentation of the effects of malnutrition. The examination begins with correct measurement techniques and use of the appropriate growth charts, as discussed earlier in this chapter. Head circumference should also be measured, as the presence of microcephaly in a child with FTT raises concern for severe malnutrition or, in the presence of neurologic signs, for congenital infections, genetic conditions, or brain injury. The physical examination should be performed with special attention to any signs of malnutrition, such as wasting of the buttocks, dry skin, and sparse hair. Wasting would not be expected in a child who is constitutionally small. Abdominal bloating or ascites with muscle wasting and edematous hands and feet is particularly suggestive of kwashiorkor, a condition that is rare in the United States. On occasion, the evaluation of a child with poor growth leads to a suspicion of child maltreatment. In this situation, the local agency for child protective services should be called.

Evaluation of the child with FTT can usually be performed in the outpatient setting. However, hospital admission may be warranted if neglect is suspected, when a patient is at risk for refeeding syndrome, or when outpatient management fails. Above-average weight gain without supplemental feeds has often been viewed as supporting a diagnosis of neglect as an underlying factor in FTT. However, it is not diagnostic, particularly as weight fluctuation can occur frequently in the early stages of refeeding. In addition, the experience of hospital admission itself adds new variables that may affect a child’s feeding behavior and serve as “confounders.”