Infant and Pediatric Growth Charts

Growth charts plot a child's anthropometric measurements - weight, length or height, head circumference, and body mass index - against age- and sex-specific reference curves, expressed as percentiles or z-scores. They are the principal tool for assessing whether an infant or child is growing as expected and for detecting under- or over-nutrition early.

Definition

A growth chart is a set of age- and sex-specific reference curves for anthropometric measurements (such as weight, length/height, head circumference, and BMI) used to position an individual child's measurement as a percentile or z-score and to monitor growth over time.

Scope

This entry covers the construction and interpretation of growth charts in nutritional assessment, including the distinction between a growth reference and a growth standard, the indicators charted (weight-for-age, length/height-for-age, weight-for-length/height, BMI-for-age, head circumference), and the use of percentiles and z-scores. It is a reference overview, not clinical guidance for individual children.

Key concepts

• Percentiles and z-scores (standard deviation scores)
• Growth reference versus growth standard
• Weight-for-age, length/height-for-age, weight-for-length/height
• BMI-for-age
• Head circumference-for-age
• Serial measurement and growth velocity
• LMS method for smoothing reference curves

Mechanisms

Growth charts are built from anthropometric data of a reference population, summarized as smooth percentile or z-score curves by age and sex; the LMS method, developed by Cole and colleagues, models the skewness, median, and variability of the distribution at each age to produce these curves. A reference simply describes how a sampled population grew, whereas a standard - exemplified by the WHO Child Growth Standards (WHO Multicentre Growth Reference Study Group, 2006) - is built from children raised under conditions thought to support optimal growth, so it prescribes how children should grow under those conditions. An individual child's measurement is converted to a percentile or z-score, and serial plotting tracks whether growth follows expected trajectories.

Clinical relevance

Growth charts are used to screen for faltering growth, stunting, wasting, underweight, and overweight, and to monitor recovery or change over time. They describe how growth is measured and classified relative to a reference or standard rather than prescribing treatment, and interpretation depends on which chart is used and on serial rather than single measurements.

Epidemiology

Standardized growth references underpin nutritional surveillance of children worldwide. The WHO Child Growth Standards for children under five (2006) and the WHO growth reference for school-aged children and adolescents (de Onis and colleagues, 2007) provide internationally applicable charts, while national references such as the UK 1990 BMI curves (Cole and colleagues, 1995) and the international child obesity cut-offs (Cole and colleagues, 2000) support consistent classification of weight status.

History

Early growth charts were national growth references derived from local survey data. A major shift came with the WHO Multicentre Growth Reference Study, which produced prescriptive growth standards (2006) based on healthy, breastfed children from several countries, complemented by a WHO reference for older children and adolescents (de Onis and colleagues, 2007). Methodological work by Cole on the LMS method enabled the smooth, statistically principled construction of these curves.

Debates

Growth reference versus growth standard - which should be used?

A reference describes how a sampled population actually grew, while a standard describes how children should grow under optimal conditions; the WHO standards adopt the prescriptive approach for young children, and the choice between reference and standard affects how growth is classified.

Key figures

• Mercedes de Onis
• Timothy Cole
• Cutberto Garza

Seminal works

• who-mgrs-2006
• deonis-2007
• cole-1995

Frequently asked questions

What is the difference between a growth reference and a growth standard?

A reference describes how a particular sampled population actually grew, while a standard describes how children should grow under conditions thought to support optimal growth, such as the WHO Child Growth Standards.

What do percentiles and z-scores on a growth chart mean?

They express how a child's measurement compares with the reference population for the same age and sex - a percentile gives the rank position, and a z-score gives the number of standard deviations from the reference median.

Why are serial measurements important on a growth chart?

A single point shows position relative to the reference, but plotting measurements over time reveals the child's growth trajectory, which is more informative for detecting faltering or excessive growth.