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Measuring and assessing child growth

Margaret Lawson
MSc PhD SRD
Senior Research Fellow in Paediatric Nutrition
Childhood Nutrition Research Centre
Institute of Child Health
London

Growth in childhood is universally acknowledged as an important indicator of health, and an infant's birth size and subsequent weight gain are noted carefully by parents. Poor growth is closely linked to suboptimal development; this is most obvious in countries where malnutrition is common,(1) but in Western countries preterm infants fed an enriched milk formula grew better and had a higher development quotient compared with slower-growing babies receiving a standard milk formula.(2) Slow growth during early life may also be detrimental to adult health.(3)

Monitoring healthy ­children
Routine measurements of growth should be carried out sufficiently frequently to detect abnormalities, but too frequent weight checks may cause anxiety for parents. Recommendations for routine measurements of healthy infants and children are set out in Health for all Children.(4)
A weight check is recommended at birth, 2, 3, 4 and 8 months, coinciding with contact visits for immunisation and health checks. If parents request additional checks, babies should be weighed no more than every fortnight up to 6 months and monthly between 6 and 12 months. A weight measurement should be carried out at 12­­­-15 months and again at school entry. In addition, infants and children should be weighed opportunistically whenever they present at a healthcare centre.
Length or height measurements are difficult to accurately measure in infants and young children. Traditionally, an infant's birth length is recorded, although length at 6-8 weeks is more predictive of later stature. There are no recommendations for routine height measurements in healthy children until school entry.(4) Head circumference should be measured at birth and again at 6-8 weeks. No routine measurement of head circumference is recommended thereafter.(4)

Measurement of infants and children
All measurements should be carried out accurately, and staff should receive training in measuring so that all procedures are carried out using the same protocol. Methods for taking measurements are given in Health for all Children,(4) and training can be arranged via the Child Growth Foundation. Scales should be regularly checked and calibrated, while electronic self-zeroing scales should be placed on a level, hard, uncarpeted surface. Increments of 10-20g are useful for weighing infants, while 100g and 200g increments are sufficient for preschool and school-age children respectively.
Supine length is measured until 2 years, and standing height thereafter. Length should be measured using a board or a mat with 0.5cm increments placed on a hard, uncarpeted surface; standing height is measured using a stadiometer with 0.5cm increments placed on a firm surface. Measurements using a tape measure are too inaccurate to be of clinical use. Head circumference is measured using a plastic or fibreglass insertion tape. The "Health for all Children" website  gives details of equipment (see Resources).
Measurements should be plotted on appropriate centile charts to monitor progress. The UK90 charts should be used for all healthy children,(5) whatever their ethnic origin,(6) and kept in the "Personal Child Health Records" (PCHR). Breastfed babies grow at a different rate from formula-fed infants; the UK90 cohort was largely formula-fed, and charts for breastfed babies are available as alternative inserts to the PCHR. They are suitable for use for all babies up to the age of 1 year.

When to be concerned about growth
Although the recommendations for routine growth monitoring suggest a minimum of five occasions in the first year, it is also recommended that more frequent measurements are made if there is any concern about the infant's or child's growth, development, nutrition or general health. Finding abnormalities in weight or length may lead to the early detection of growth-limiting conditions such as Turner's syndrome, or assist in the diagnosis of chronic conditions such as cystic fibrosis. Growth faltering without organic illness occurs in 5% of infants in the UK, and early intervention improves outcome.(7) Excessive weight gain in infancy and early childhood is associated with later obesity.(8)
Interpretation of growth data is important: growth velocity varies, and many children cross centile charts as part of their normal growth pattern. Table 1 lists situations where closer growth monitoring is indicated. There is a tendency for babies' weight and length to move towards the 50th centile: healthy, large babies may cross centiles downwards, while smaller babies are more likely to cross centiles in an upward direction. An aid to the interpretation of centile crossing are the "thrive lines",which define the upper and lower limits of normal weight gain.(9) Two sets of thrive lines are available as acetates that overlay the PCHR and A4 weight charts. The 5% thrive lines define the lower limits of normal weight gain. An infant following the 5% thrive lines or moving downwards from a thrive line is growing ­unusually slowly. The 95% thrive lines define the upper limits of normal weight gain, and an infant tracking or moving upwards from them is gaining weight excessively quickly. Where there is concern about a child's weight gain, a length or height measurement should be taken at the same time, as weight and height centiles are similar.

[[NIP15_table1_29]]

Height and weight charts do not assess body fatness. In adults, optimum health is associated with a body mass index or BMI (weight/height2) of 20-25kg/m(2). In infants and children, the body fat content and therefore the BMI varies naturally according to age. Age-specific BMI centiles have been developed and are useful in identifying children with a high or low proportion of body fat.(10) Children who are abnormally thin will have a BMI below the 9th centile. The international task force on obesity has suggested that a BMI above the 91st centile is defined as overweight, and that one above the 98th centile is defined as obese.(11) The use of waist circumference centile charts helps to distinguish between a high BMI due to lean or muscle tissue and one that is due to excess adipose tissue.(12)

Conclusion
Routine measurement of healthy children reassures parents about their child's health. The primary care nurse should be alert for signs that growth is disturbed and implement more frequent measurements of body size. Correct interpretation of growth data will enable the early detection and treatment of some conditions associated with abnormal gains in weight and height.

References

  1. Walker SP, et al. Effects of growth restriction in early years on growth, IQ cognition at 11-12 years and the ­benefits of nutritional supplementation and psychosocial stimulation. J Pediatr 2000;137:36-41.
  2. Lucas A, et al. Randomised trial of early diet in preterm babies and later intelligence quotient. BMJ 1998;317:1481-7.
  3. Lucas A, et al. Fetal organs of adult disease - the hypothesis revisited.BMJ 1999;319:245-9.
  4. Hall DM, Elliman D, editors. Health for all children. 4th ed. Oxford: Medical Publications; 2003.
  5. Wright CM, et al. Growth reference charts for use in the United Kingdom. Arch Dis Child 2002;86:11-4.
  6. Kelly AM, et al. Growth of Pakistani children in relation to the 1990 growth standards. Arch Dis Child 1997;77:401-5.
  7. Wright CM. Identification and management of failure to thrive:a community perspective.Arch Dis Child 2000;82:5-9.
  8. Stettler N, et al. Rapid weight gain in infancy and obesity in young adulthood in a cohort of African Americans.Am J Clin Nutr 2003;77:1374-8.
  9. Cole TJ. Conditional reference charts to assess weight gain in British children. Arch Dis Child 1995;73:8-16.
  10. Cole TJ, et al. Body mass index reference curves for the UK.Arch Dis Child 1995;73:25-9.
  11. Cole TJ, et al. Establishing a ­standard definition for child overweight and obesity worldwide: international survey. BMJ 2000;320:1240-3.
  12. McCarthy HD, et al. The ­development of waist circumference percentiles in British children aged 5-16.9 years. Eur J Clin Nutr 2001;55:902-7.

Resources
Health for Children
W:www.health-for-all-children.co.uk
Includes details of equipment and growth charts relevant to ­paediatric ­practice, and links to other relevant websites
The Child Growth Foundation
2 Mayfield Avenue,
London
T:0208 995 0257
E:cgflondon.aol.com
Provides advice on measuring equipment and runs training sessions in ­measurement techniques
Harlow Printing
W:www.harlowprinting.co.uk
Publishes the Child Growth Foundation UK90 charts and thrive- line acetates