Failure to thrive

Published on 21/03/2015 by admin

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Chapter 16 FAILURE TO THRIVE

Jonathan M. Wong and Timothy J. Horita

General Discussion

Failure to thrive (FTT) is a descriptive term and not a specific diagnosis. FTT is best defined as inadequate physical growth diagnosed by observation of growth over time using a standard growth chart. Most practitioners diagnose FTT when a child’s weight for age falls below the fifth percentile of the standard National Center for Health Statistics (NCHS) growth chart or if it crosses two major percentile lines.

Average birth weight for a term infant is 3.3 kg (7.27 lb). Weight declines as much as 10% in the first few days of life, probably as a result of loss of excess fluid. Birth weight should be regained within 2 weeks after birth. Breast-fed infants tend to regain birth weight a little later than bottle-fed infants. Term infants double their birth weight by age 4 months and triple their birth weight by age 12 months.

Term infants grow approximately 25 cm in length during the first year, 12.5 cm in the second year, and then slow down to about 5 to 6 cm per year between age 4 and the onset of puberty, at which time growth can increase up to 12 cm per year. Average head circumference is 35 cm at birth and increases rapidly to 47 cm by age 1 year. The rate of growth then slows, reaching an average of 55 cm by age 6 years.

Adjusted growth curves for different populations exist, including those for premature infants, Down syndrome, Turner syndrome, meningomyelocele, intrauterine growth retardation, low birth weight, and very low birth weight. While plotting growth charts for premature patients, a “corrected age” is used when using a standard growth curve. This corrected age is calculated by subtracting the number of weeks of prematurity from the postnatal age (gestational age). This corrected age should be continued with subsequent measurements because it may take an average of 18 months to catch up on head circumference, 24 months for weight, and 40 months for height.

Accurate measurements are essential to the interpretation of growth charts. Scales need to be calibrated regularly, and it helps to use the same machines, if possible, for consecutive measurements. Similarly, lengths should be measured carefully, and head circumference should be measured using standardized techniques.

As long as the patient is growing along a curve (albeit at a lower percentile), FTT should not be diagnosed. Growth variation in normal infants can confound the diagnosis of FTT. About 25% of children will shift their weight or height downward by more than 25 percentile points in the first 2 years of life. These children are falling to their genetic potential or demonstrating constitutional growth delay. After shifting downward, these infants grow at a normal rate along their new percentile and do not have FTT.

In the United States, reports from 1980 to 1989 indicate that FTT accounted for 1% to 5% of tertiary hospital admissions for infants younger than 1 year. This probably represents an underestimation, however, because most children with FTT are not admitted to the hospital. An estimated 10% of children in primary care settings show signs of FTT. In underdeveloped countries, FTT is more common, with malnutrition manifesting as FTT.

Ultimate physical growth may be decreased in children with FTT. Cognitive development is affected in children younger than 5 years who have FTT. Even with improvement of nutritional status, these deficits might not be completely reversed. Traditionally, it had been thought that nonorganic causes of FTT, such as neglect, resulted in more cognitive deficits than organic causes, such as gastrointestinal absorptive problems. In developing countries, malnutrition is a significant cause of mortality, whether directly or secondary to complications such as infection.

FTT can occur in all socioeconomic strata, although it is more frequent in families living in poverty. Studies indicate an increased incidence in children receiving Medicaid, children living in rural areas, and homeless children. Nonorganic FTT is more commonly reported in females than in males.

Causes of Failure to Thrive

Traditionally, FTT has been divided into organic and nonorganic causes. This distinction is not used as often because most children with FTT have mixed causes. A child with a medical disorder may develop feeding problems, which can cause family stress, which then further compounds the feeding problem. Nonorganic causes may also result from environmental factors, psychological factors, an abnormal interaction between the caregiver and child, or maternal rejection or neglect of the child. A malnourished mother or mother with an eating disorder may also result in a child having FTT. Likewise, family dysfunction, a difficult child, or poor parental feeding skills may lead to FTT.

More recently, the classification of FTT has been based on pathophysiology: inadequate caloric intake, inadequate absorption, excess metabolic demand, or defective utilization.

Inadequate Caloric Intake

Inadequate Absorption

Increased Metabolism

Chronic infection

• Human immunodeficiency virus (HIV)

• Other immunodeficiencies

Hyperthyroidism

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