GUIDE
The WHO growth charts are recommended for babies 0-2 years. They're based on healthy breastfed babies and show how babies should grow. CDC charts are designed for ages 2-20 and show how a US reference population did grow. Using the wrong chart can misclassify your baby's growth.
The chart your pediatrician uses can shift your baby's percentile by 10-15 points. That matters.
Track percentiles the right way
“In the first two years of life, it's hard to predict what a child's growth chart will look like. Babies hit many growth spurts. After age 2, we have a better sense of how they are trending in their growth and where they may eventually settle.”
Dr. Minh-Y Canh, DO, Pediatrician, Cleveland ClinicA lot of parents assume all growth charts are basically the same. They are not. The WHO and CDC growth charts were built from different populations, with different methodologies, and they answer fundamentally different questions.
The WHO growth standards (released 2006) were created from a carefully selected group of healthy, breastfed babies from six countries. These babies were raised in optimal conditions — adequate nutrition, non-smoking mothers, and breastfeeding for at least 12 months. The resulting charts show how babies should grow when everything is going right. They are a prescriptive standard.
The CDC growth charts (updated 2000) were created from US national health survey data collected between 1963 and 1994. This population included both breastfed and formula-fed babies, with a heavy skew toward formula-fed infants (reflecting feeding practices of that era). The charts show how American babies did grow. They are a descriptive reference.
This distinction matters because a descriptive reference includes unhealthy growth patterns in its "normal" range. The CDC charts were built from a population where obesity rates were already rising and breastfeeding rates were low. Using them as the standard for infant growth means comparing your baby against a population that may not represent optimal health. This is especially important if you're tracking breastfed vs. formula-fed growth differences, since the CDC population skewed heavily toward formula feeding.
| Aspect | WHO Growth Standards | CDC Growth Charts |
|---|---|---|
| Population studied | Healthy breastfed babies from 6 countries (Brazil, Ghana, India, Norway, Oman, US) | US reference population — mixed feeding methods, collected 1963-1994 |
| What it represents | How babies should grow under optimal conditions (prescriptive standard) | How a specific US population did grow (descriptive reference) |
| Recommended age range | Birth to 2 years (charts extend to 5 years) | 2-20 years (infant charts exist but are not recommended for 0-2) |
| Breastfed baby accuracy | Designed for breastfed babies — accurate representation of their growth pattern | Overrepresents formula-fed babies — can make breastfed babies appear small |
| Overweight detection | Identifies overweight earlier — more sensitive to excess weight gain | Higher thresholds — may miss early signs of excess weight gain in infants |
| Underweight detection | Less likely to over-diagnose underweight in breastfed babies | May falsely flag breastfed babies as underweight after 6 months |
| AAP recommendation | Recommended for all babies 0-2 years | Recommended for children 2-20 years |
WHO charts are the gold standard for infant growth assessment worldwide.
These are minor logistical issues — the clinical accuracy of WHO charts for infants is well-established.
CDC charts are excellent for children 2-20 — they just shouldn't be used for infants.
The primary concern: using CDC charts for infants can lead to unnecessary worry or missed issues.
Tinylog uses WHO growth standards for babies 0-2 — the charts recommended by the AAP and WHO. Log weight, length, and head circumference and see accurate percentiles without chart confusion.
Here is a real scenario that plays out in pediatric offices daily: a breastfed baby is growing perfectly along their own curve on WHO charts. At the 6-month visit, the office software uses CDC charts. Suddenly the baby appears to have "dropped" from the 50th to the 35th percentile. The pediatrician mentions it. The parent panics. Supplementation with formula is discussed.
But the baby didn't change. The chart changed. The breastfed growth pattern — where weight gain naturally slows after 4-6 months — is reflected accurately on WHO charts but can look like a decline on CDC charts. If you've been told your baby has dropped percentiles, make sure you know which chart is being used before worrying. This is because the CDC reference population includes heavier formula-fed babies who continue gaining weight at a faster rate.
The CDC itself recognized this issue and has recommended WHO charts for children under 2 since 2010. But not all pediatric offices have made the switch. Electronic health record systems sometimes default to CDC charts. If your baby's percentile seems to have dropped and you're not sure which chart is being used, ask. For premature babies, neither standard chart is appropriate in the NICU period — Fenton growth charts are the correct choice for preemies.
At your next well visit, ask whether your doctor is using WHO or CDC charts for your baby under 2. If they're using CDC, ask about switching to WHO. Some practices haven't updated their systems, and a polite question can prompt the change.
Whether using WHO or CDC, a single percentile reading means very little. What matters is the trend over time. A baby consistently at the 20th percentile is growing fine. A baby who drops from the 60th to the 20th over two visits warrants investigation.
Don't switch between WHO and CDC charts between visits. The percentiles aren't directly comparable. Pick one (WHO for under 2, CDC for 2+) and stick with it for consistent tracking.
This guide is for informational purposes only and is not a substitute for professional medical advice. Consult your pediatrician for guidance specific to your baby.
