Growth Charts and Anthropometry
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Direct answer
Growth charts and anthropometry compare weight, length or height and head circumference with a reference population of the same age and sex. The WHO Child Growth Standards of 2006 are prescriptive for children under five, while IAP charts describe Indian children, so the chart chosen can change a diagnosis. Serial measurements plotted over time, rather than a single value, establish whether growth is abnormal.
What you must remember
- Z-score: the number of standard deviations a value lies from the median for age and sex; below minus 2 is the usual threshold for underweight, stunting and wasting.
- Standard versus reference: the WHO 2006 standards are prescriptive for under-fives; the WHO 2007 reference describes how children of 5 to 19 years grow.
- Recumbent length: children under 2 years are measured lying down, and standing height is recorded later.
- Birth weight course: physiological loss of up to about 10 per cent in the first week is regained by 10 to 14 days, after which weight doubles by about 5 months and triples by 1 year.
- Length course: length rises from about 50 cm at birth to about 75 cm at 1 year, a gain of roughly 25 cm in the first year.
- Head circumference: it grows fastest in the first year, from about 34 to 35 cm at birth to about 46 cm at 1 year, and it serves as a proxy for brain growth.
- Mid-parental target height: add the parents' heights, add 13 cm for a boy or subtract 13 cm for a girl, then divide by two; the expected adult height lies within about 8.5 cm either side.
Reading a child who is falling behind
A 14-month-old boy is brought because his weight has slipped from the 50th to the 10th centile over six months, while his length has stayed on its line. The pattern of which indices fall tells the examiner what has happened, as summarised below.
| Index | What it reflects | Usual cut-off |
|---|---|---|
| Weight-for-age | Underweight, mixed picture | Below minus 2 SD |
| Length or height-for-age | Stunting, longer-standing insult | Below minus 2 SD |
| Weight-for-length or height | Wasting, recent or acute loss | Below minus 2 SD; severe below minus 3 SD |
| BMI-for-age | Thinness or overweight | Thinness below minus 2 SD; overweight above plus 1 SD at 5 to 19 years |
Wasting with normal length points to a recent illness or poor intake, so the child needs a weight-for-length check before any longer-term label. Stunting with normal weight-for-height suggests a chronic or earlier problem that has affected linear growth over time. Mid-parental height and the child's own growth velocity then help separate a constitutional pattern from true pathology.
Where the exam tries to catch you
Most growth questions turn on a measuring or plotting error rather than on a rare disease.
- Trap: plotting a 30-week preterm infant at chronological age. Correct: use corrected age, subtracting the weeks born early, until about 2 years, or the infant looks wrongly stunted or underweight.
- Trap: measuring a 15-month-old's height standing up. Correct: recumbent length is used before 2 years, because standing height is not comparable with the WHO length curve.
- Trap: calling one low weight faltering growth. Correct: faltering means crossing two major centile lines downward over serial visits; a single value needs repeat measurement first.
- Trap: calling a 10 per cent fall in birth weight in week one abnormal. Correct: physiological loss is expected in the first week; failure to regain birth weight by 10 to 14 days needs a feeding review.
Frequently asked questions
Which growth chart is used for Indian children under five?
The WHO Child Growth Standards are the reference used in national nutrition programmes for children under five. IAP charts, built on Indian children, are often used for school-age children.
What is the difference between a growth standard and a growth reference?
A growth standard, such as the WHO 2006 charts for under-fives, describes how healthy children should grow and is applied prescriptively. A growth reference describes how children in a population actually grow, and the WHO 2007 reference for 5 to 19 years is used descriptively.
How is mid-parental target height calculated?
Add the father's and mother's heights in centimetres, add 13 for a boy or subtract 13 for a girl, and divide the total by two. The expected adult height lies within about 8.5 cm either side of this figure, so a child far outside that band needs evaluation.
How much weight loss is physiological in a newborn?
A newborn may lose up to about 10 per cent of birth weight in the first week without disease, particularly when breastfed. Regaining birth weight by 10 to 14 days is expected, and failure to regain it, or a continuing fall, needs a feeding review.
When is length measured lying down?
Recumbent length is measured on a length board in children below 2 years, because they cannot stand reliably. Standing height is measured after 2 years.