Standards, birth to 2
The WHO growth chart, and why infants get their own
For the first two years, the world's pediatric community reads growth against a different kind of curve — a standard, not a survey.
The WHO Child Growth Standards (birth to age 2 in GrowTall) describe how healthy children grow under optimal conditions, based on a multicentre study across six countries with breastfed infants as the normative model. They are prescriptive standards, not just population averages.
How the standards were built
The WHO Child Growth Standards came out of the Multicentre Growth Reference Study (1997–2003), conducted in Brazil, Ghana, India, Norway, Oman and the United States. Rather than averaging whatever children happened to measure, the study enrolled children in favorable health conditions — notably breastfed infants, non-smoking households, and adequate care — and described how they grow.
Standard vs. reference — why the difference matters
A reference (like the CDC 2000 charts) describes a population as it was measured. A standard describes a norm: how children grow when things go well. For infants, the WHO standard is generally considered the better yardstick — healthy, breastfed babies across six very different countries grew remarkably similarly.
One practical consequence: a baby tracking on the WHO curves is following the normative pattern, not merely blending into a national average.
Length, not height
Infants are measured lying down — recumbent length — crown to heel, on a firm surface with legs gently extended. Length reads about 0.7–1 cm longer than standing height, which is one reason the reference switches at age 2. GrowTall's measurement guidance changes with the profile's age so the right protocol is used. See how to measure height.
WHO curves in GrowTall
From birth to under age 2, GrowTall plots length-for-age on WHO standards and computes the percentile; from age 2 it transitions to CDC curves automatically. The same profile, the right reference at the right age — and a seamless history across the switch.
Common questions
Why are breastfed infants the WHO model?
Breastfeeding was the reference feeding pattern in the study because it is the physiological norm for infants, and it is associated with the healthy growth pattern the standards describe. Formula-fed babies can also grow perfectly healthily — the curves remain a screening context for everyone.
When do we switch from WHO to CDC curves?
At age 2, when measurement switches from recumbent length to standing height. GrowTall makes the switch automatically and keeps the history continuous.
Does WHO publish curves beyond age 2?
Yes, WHO also publishes growth references for ages 5–19. GrowTall uses the CDC 2000 reference for ages 2–20, which is the convention many pediatric settings follow.
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