Growth and Failure to Thrive

According to Medline Plus:

"Failure to thrive is a description applied to children whose current weight or rate of weight gain is significantly below that of other children of similar age and sex."¹

It is a term that tends to be applied to young children, especially babies rather than older children or teenagers. Failure to thrive (FTT) is a descriptive term or cause for concern. It is not a disease and so a cause must be sought.

This definition is, quite appropriately, rather loose. It does not specify being below the 2nd, 5th or 10th centile, as this would, by definition, include 2, 5 or 10% of all babies, even without pathology. Hence it is impossible to give meaningful figures for incidence but it is a fairly common problem.

What is more important than a single measurement is falling through the centiles.

When assessing growth in all children, both height and weight should be considered and in small children, head circumference too.

To diagnose failure to thrive it is imperative to understand normal growth and variation. For example, it is normal for a baby to lose up to 10% of body weight in the first few days of life. This is rapidly regained but more slowly in breast fed babies. In our quest to avoid FTT it is important not to encourage obesity in children instead.

For premature babies, a "corrected age" should be used, based on time since birth minus degree of prematurity. Thus a baby who was born 12 weeks ago at 32 weeks gestation is treated as a 4 weeks old baby. Growth charts based on gestational age rather than chronological age are available for infants from 26 weeks' gestational age but they are synthesized from a relatively small number of infants with variable problems and so they should be treated with caution.²

A premature baby should have reached "normality" for head circumference at around 18 months, weight at about 24 months and height at above 40 months. Thereafter normal charts may be employed but some premature babies with very low birth-weight do not catch up until 5 or 6 years old.

There are also specific reference charts for Down's syndrome and Turner's syndrome.

Diagnosing that abnormality exists is fundamental to this issue and it is discussed in much more detail in Centile Charts and Assessing Growth. This article will focus instead upon the many causes of failure to thrive.

There are separate centile charts for boys and girls as the former tend to be bigger. There may well be some racial differences too. Children of Indian race are often a little smaller than those of European origin and it is inappropriate to cause undue concern over a child who is obviously happy and well. Look at the parents. Tall parents have tall children and short parents have short children. Obesity is an acquired rather than a hereditary condition, although some genetic aspects are discussed in Obesity - the Size of the Problem.

The genetic component of height and weight tend to become manifest between birth and 2 years of age. Hence children of small parents may fall through the centile charts. The height and weight should be on roughly the same centiles and look at the height of the parents. Radiological bone age is also normal. About 25% of normal children will shift to a lower centile line in the first 2 years of life. If there are small parents and a healthy, happy child, there is no cause for concern.³

Look at the charts but do not forget to look at the child.

Start by looking at the history of the pregnancy with regard to:

• Smoking
• Alcohol consumption
• Use of medications
• Any illness during the pregnancy

As a general rule, placental insufficiency will lead to a small-for-dates baby who emerges hungry and eager to feed.

• Examine infant feeding.
  • With bottle fed babies it is easy to see exactly how much is taken at each feed.
  • With breast feeding this is much harder without test feeding.
  • Does the child seem content with the feed, dissatisfied and craving more or disinterested?
• Ask about the frequency of wet nappies and dirty nappies.
• Ask about the nature of the stool.
  • Remember that it is highly variable in quality and quantity in small babies, especially if breast fed.
  • Chronic diarrhoea will result in failure to gain weight.
• Ask about illness in the child. Meningitis, fits and cerebral palsy may all cause or indicate problems.
• Note how the mother interacts with the child. Is she caring and concerned or cold and distant?

Look at the baby.

• Does this look a healthy, lively and active child?
• Are there any features suggestive of a syndrome such as Downs syndrome or Turner's syndrome?
• Does the child look well-nourished or starved?
• Note any other obvious features such as:
  • Cyanosis
  • Tachypnoea
  • Jaundice
• When picked up, does muscular tone feel normal and does the baby respond as if used to affection?
• Is the child alert and responsive?

Plot height, weight and head circumference on a chart. If possible, plot earlier readings too as trends or falling through the centiles are much more important than isolated readings.

Note pulse rate and respiratory rate. Possible blood pressure and even arterial blood gases are required. Blood gas analysis may prevent excessive diagnosis of renal tubular acidosis.⁴

Other physical signs may include:

• Oedema
• Hepatomegaly
• Rash or skin changes
• Hair colour and texture abnormalities
• Signs of vitamin deficiency

Marasmus is pure calorie malnutrition but it can mimic dehydration. Features of dehydration include:

• Decreased skin turgor
• Sunken anterior fontanelle
• Dry mucous membranes
• Absence of tears
• Acutely ill appearance

There are a very wide range of causes of FTT and more than one may be applicable.

Pre-natal causes of FTT include:

• Prematurity with complications
• Maternal malnutrition
• Toxic exposure in utero, including alcohol, smoking, medications, infections
• Intrauterine growth retardation
• Chromosomal abnormalities

IUGR often produces a small but hungry and eager baby. However, a combination of pre-term and small-for-dates is more likely to cause difficulties.

Toxins in utero may include tobacco, drugs of abuse, especially amphetamines and cocaine and alcohol. Fetal alcohol syndrome may occur or the incomplete fetal alcohol effects. Infection in utero may include rubella, toxoplasmosis and cytomegalovirus.

Postnatal causes include lack of adequate intake of nutrition:

• Lack of appetite may occur with iron deficiency anaemia, CNS pathology and chronic infection
• Inability to suck or swallow, especially with CNS or muscular disorders
• Vomiting due to CNS or metabolic diseases, obstruction or renal disorders
• Gastro-oesophageal reflux and oesophagitis

Physical problems of feeding may occur with cleft palate, hypotonia, micognathia and Prader-Willi syndrome.

Poor absorption or metabolism of nutrients occurs with:

• Gastro-intestinal disorders including cystic fibrosis, coeliac disease and chronic diarrhoea
• Renal failure or renal tubular acidosis
• Endocrine abnormalities including hypothyroidism, diabetes mellitus, growth hormone deficiency
• Inborn errors of metabolism
• Chronic infection including congenital HIV, tuberculosis, parasites

Increased metabolic demand occurs with:

• Hyperthyroidism
• Chronic disease such as heart failure and broncho-pulmonary dysplasia
• Renal failure
• Malignancy

Non-organic or "functional" causes of FTT may include:

• Poor feeding, possibly caused by ignorance and lack of supervision and help (no friends, no extended family). Are feeds made up properly?
• Lack of preparation for parenting
• Family dysfunction (eg, divorce, spouse abuse, chaotic family style)
• Difficult child
• Child neglect (there may be puerperal depression)
• Emotional deprivation syndrome
• The mother may have an eating disorder but more often they tend to over-feed the rest of the family
• Munchausen syndrome by proxy

Investigations are usually guided by history and examination. Routine tests may include:

• FBC
• Urinalysis
• Urine culture
• U&E and creatinine
• LFTs, including total protein and albumin
• Prealbumin may be used as a nutritional marker

The following tests are not usually routine but may be indicated by history and examination:

• Testing for HIV infection
• Sweat chloride test
• Thyroid function tests
• Stool studies for parasites or malabsorption
• Immunoglobulins
• Purified protein derivative (PPD) skin test (for tuberculosis)
• Radiological studies (bone age may be helpful to distinguish genetic short stature from constitutional delay of growth)

Special tests may be used for coeliac disease or to detect growth hormone deficiency.

Look for problems in the mother as well as problems in the child. Puerperal depression may present with the child failing to thrive.

Management will depend upon the underlying cause.

• With syndromes such as Turner's or Downs, it may be that use of the correct charts shows that growth is as expected.
• Physical illness such as cyanotic congenital heart disease, cystic fibrosis or coeliac disease needs treating accordingly.
• High calorie feeding may be required but this needs specialist help or overloading the gut causes diarrhoea and is counterproductive.
• If the mother is not coping she needs help and advice with plenty of input from the health visitor.⁵ It may be necessary to remove the baby, especially in Munchausen syndrome by proxy, but this should not be done without considerable thought and attempts to rectify the situation.
• The potential value of a specialist health visitor is uncertain.⁶
• If improvement in the community is inadequate, admission to hospital may permit more intense observation and support. If the child thrives under these conditions, it is highly suggestive of poor parenting skills.
• Puerperal depression may need to be treated. Support and supervision is needed in the meantime.
• The baby may need to be put on the at risk register with multidisciplinary input until such time as it is deemed safe to remove the name.

There is a fear that failure to thrive may result in long term stunting of growth and cognitive developmental delay. This may be compounded if there is emotional neglect too.⁷ However, when corrections are made for maternal IQ, cognitive impairment does not appear to be so much of a problem as was thought.⁸ Long term effects on height and weight appear to be more marked than on IQ.⁹

As a general rule, if small babies double their birth weight in 4 months and triple in a year, they will catch up.

A systematic review concluded that the long term outcome of FTT is a reduction in IQ of about 3 points, that is not of clinical significance.¹⁰

• Good antenatal care and avoidance of toxins such as illicit drugs, tobacco and alcohol in pregnancy will reduce the risk.
• Parenting classes should lead to a better understanding of the needs of the baby. Nowadays fathers are often involved too and this is to be welcomed.
• An astute midwife or health visitor should detect problems before they become serious.

The general practitioner and primary healthcare team are in a difficult position and have to strike a balance between being accused of failure to recognise FTT¹¹ and causing excessive and unnecessary alarm over healthy babies.