WHO vs. CDC Growth Charts: Which One Is Right for Your Baby?
There are two major infant growth chart standards in use in the United States, and they are not interchangeable. The American Academy of Pediatrics recommends WHO growth charts for all children under 2 — and for breastfed babies, the difference between the two charts is clinically significant. Here is what you need to know.
The Key Difference Between WHO and CDC Charts
The WHO Child Growth Standards, published in 2006, were built from a landmark study of children in six countries (Brazil, Ghana, India, Norway, Oman, and the United States) raised in optimal conditions: predominantly breastfed, non-smoking households, adequate nutrition. The data describes how children grow when they are growing well. It is a prescriptive standard — it tells you what growth should look like.
The CDC growth charts, published in 2000, are built from U.S. population data collected between 1963 and 1994 — a period when formula feeding was predominant and breastfeeding rates were low. The CDC charts are descriptive: they reflect how American children actually grew during that era, not how children grow under optimal conditions.
WHO vs. CDC Charts at a Glance
Why It Matters for Breastfed Babies
Breastfed and formula-fed babies do not grow at the same rate, and this difference is not random — it is physiological. According to research published in Pediatrics (AAP), breastfed babies grow faster in the first 3-4 months and then slow after month 4 — a natural, healthy pattern. Formula-fed babies tend to gain weight more rapidly throughout the first year.
When breastfed babies are plotted on CDC charts (which were built primarily from formula-fed data), the deceleration after month 4 can look like a concerning drop on the chart. Parents and even some clinicians may interpret this as a feeding problem — when in fact the baby is growing exactly as expected for a breastfed infant.
WHO charts, built from breastfed babies, accurately represent this growth pattern. A breastfed baby who looks like they are “falling off the curve” on a CDC chart may plot perfectly normally on a WHO chart — because the WHO chart was built from babies who grew the same way.
What Percentiles Actually Mean
Percentiles are not grades. A common source of parental anxiety is misinterpreting a low percentile as a sign that something is wrong.
A percentile simply describes where your baby falls in the reference distribution. A baby at the 15th percentile for weight is larger than 15% of babies their age and smaller than 85%. This is entirely within the normal range — by definition, 15% of healthy, normally growing babies are at or below the 15th percentile.
The clinically normal range on both WHO and CDC charts is the 3rd to 97th percentile. Babies below the 3rd percentile or above the 97th percentile may warrant closer monitoring, but even this does not automatically indicate a problem — some healthy babies are naturally at the extremes.
The Two-Percentile-Crossing Rule
What pediatricians actually watch for is not a specific percentile number — it is the trajectory. A baby who is consistently at the 20th percentile and growing smoothly along that curve is growing normally. A baby who was at the 60th percentile and drops to the 20th percentile over several months is crossing major percentile lines, which warrants investigation.
The clinical standard is that crossing two or more major percentile lines downward (the major lines are the 3rd, 10th, 25th, 50th, 75th, 90th, and 97th) is a signal to investigate further. A single lower measurement at one visit, especially if the baby was sick or the measurement technique varied, may not represent a real trend.
This is why tracking weight at home between visits — and seeing the trend rather than just one number — gives parents and pediatricians better information. See our article on newborn weight loss after birth for more on the early weight tracking milestones.
Preterm Babies: Corrected Age
For babies born before 37 weeks gestation, neither WHO nor CDC charts should be applied using the baby's chronological age without adjustment. Preterm babies must be plotted using their corrected age — chronological age minus the weeks of prematurity.
A baby born at 32 weeks who is now 4 months old has a corrected age of approximately 2 months (4 months minus 2 months of prematurity). They should be plotted on the chart at the 2-month point, not the 4-month point. This correction is typically used until age 2 for weight and length, and until age 3 for head circumference in very preterm babies.
LilSense handles corrected age automatically when you enter a birth date and gestational age — your baby's growth curve uses the appropriate corrected age without you needing to calculate it.
LilSense uses WHO growth charts — the same standard your pediatrician should be using
Track your baby's weight in LilSense and see where they fall on a WHO-standard growth curve. Corrected age for preterm babies is handled automatically. You'll see the trend across visits, not just a single point — which is what actually matters.
Download Free on iOSHow to Read a Growth Chart with Your Pediatrician
At well-baby visits, your pediatrician will plot your baby's measurements and show you where they fall. Here are the questions worth asking:
- “Which chart are you using?” — Confirm it is the WHO chart for a baby under 2. If your baby is breastfed and the CDC chart is being used, the comparison may not be accurate for your baby.
- “What is the trend over time?” — A single percentile is less informative than the trajectory across visits. Is your baby tracking consistently along the same curve, or drifting?
- “Are you using corrected age?” (if your baby was preterm) — Make sure the measurement is being plotted at the corrected age, not chronological age.
- “Is the growth proportional?” — Weight, length, and head circumference should be tracking in a similar range relative to each other. A baby who is at the 10th percentile for weight but the 50th for length may have proportionality worth examining.
Frequently Asked Questions
Should my pediatrician use WHO or CDC growth charts?
The American Academy of Pediatrics recommends WHO growth charts for all children ages 0-2 years. The WHO charts were built from breastfed babies in optimal conditions and represent a prescriptive standard of healthy growth. CDC charts, built from mostly formula-fed U.S. population data from 1963-1994, are recommended for children 2 years and older.
What does baby growth percentile mean?
A growth percentile describes where your baby falls relative to a reference population. A baby at the 25th percentile is larger than 25% of babies and smaller than 75% of babies of the same age and sex. Percentile is not a grade — any value from the 3rd to the 97th percentile is considered within the normal range. The 50th percentile is not a goal; it is simply the median.
Is the 10th percentile bad for a baby?
No. The 10th percentile is well within the normal range. Some babies are naturally small, just as some are naturally large. What pediatricians monitor is consistency of the growth curve, not the absolute percentile. A baby consistently at the 10th percentile who is healthy, feeding well, and meeting developmental milestones is not a concern.
Why does my breastfed baby look like they're falling behind on the growth chart?
This is a well-documented issue when CDC charts — built primarily from formula-fed babies — are used for breastfed babies. Breastfed babies naturally slow their weight gain after month 4, which can look like a drop on a CDC chart. WHO charts, built from breastfed babies, accurately represent this pattern. If your breastfed baby appears to be “falling off the curve,” ask your pediatrician to plot the measurements on a WHO chart.
What is a growth chart?
A growth chart is a reference tool that compares a child's weight, length, and head circumference against a large population of children of the same age and sex. It shows percentile curves that help pediatricians assess whether a child is growing proportionally and consistently over time. Growth charts are one clinical input — not a standalone diagnostic tool.