Pediatric Growth Assessment: WHO, CDC, and Specialty Growth Charts Explained

Summary

• Use WHO growth charts for children younger than 2 years and CDC growth charts for children 2 years and older, per CDC, NIH, and AAP recommendations [1,2].
• The 2026 AAP/NASPGHAN guideline replaces "failure to thrive" with "faltering weight" and defines it by z-score criteria rather than percentile cutoffs alone [3].
• Faltering weight: weight-for-length or BMI-for-age less than −1.65 z-score (5th percentile), weight gain velocity less than −2 z-score (2.3rd percentile) in children under 2 years, or a decline in weight, weight-for-length, or BMI ≥1 z-score [3].
• Preterm infants (extremely preterm <28 weeks, very preterm 28 to <32 weeks) require age correction through 36 months corrected age; chronologic age alone misclassifies up to 72.9% as stunted and 89.8% as underweight at term-equivalent age [4].
• Growth velocity, not a single percentile, is the more sensitive signal for pathology. Height deviating more than two major percentile lines is abnormal [5].
• Genetic syndromes (Down syndrome, Turner syndrome, achondroplasia) require condition-specific charts in parallel with standard charts [6-9].

Caution. Switching growth chart references mid-follow-up (WHO to CDC at age 2, or preterm to standard charts) produces an artifactual percentile or z-score shift that can look like a real growth problem in a child who is in fact stable [10].

WHO vs. CDC Growth Charts

Clinical implications of chart choice:

• First 3 months of life: WHO charts show faster expected weight gain than CDC charts, so more infants appear to be growing slowly on WHO charts.
• After approximately 3 months: formula-fed infants tend to gain weight faster and may cross upward on WHO percentiles, risking misclassification as overweight.
• Ages 6-23 months: WHO charts identify fewer U.S. children as having inadequate weight-for-age than CDC charts.

Using the wrong reference risks unnecessary workup for nonexistent pathology, or missed identification of a true growth problem.

When screening for abnormal growth on WHO charts, use ±2 SD (2.3rd and 97.7th percentiles) as thresholds, not the 5th and 95th percentiles [1,2].

Open the WHO Growth Calculator → Open the CDC Growth Calculator →

Caution. The abrupt WHO-to-CDC switch at age 2 years causes a clinically significant shift even in children with stable growth: mean BMI-for-age z-score drops by 0.59 at the transition, and 28.3% of children show a BMI z-score drop greater than 1.0. Gradual-transition charts, using a weighted average from ages 2 to 5 years, reduce this artifact [10].

Z-Scores vs. Percentiles

The 2026 AAP guideline recommends z-scores over percentiles [3]:

• Z-scores are the global standard for reporting nutritional status.
• Z-scores have no upper or lower bound, so measurements below the 1st percentile can be described precisely.
• A 1-point change in z-score reflects the same magnitude of change regardless of starting point, unlike percentiles.
• Z-scores allow population comparison and more precise tracking of treatment response.

A z-score of 0 corresponds to the 50th percentile. A z-score of −2 corresponds to the 2.3rd percentile.

Faltering Weight: Diagnostic Criteria

The 2026 AAP/NASPGHAN Clinical Practice Guideline defines faltering weight as any of the following [3]:

• Weight-for-length or BMI-for-age less than −1.65 z-score (5th percentile)
• In children younger than 2 years, weight gain velocity less than −2 z-score for age (2.3rd percentile)
• Decline in weight, weight-for-length, or BMI ≥1 z-score

Not all children meeting these criteria have undernutrition [3]:

• Children born large for gestational age commonly show early z-score declines as they regress toward genetic potential. This is physiologic.
• Children with genetic conditions may have a different intrinsic growth potential.

The guideline recommends against routine diagnostic testing in the initial workup of faltering weight in children without specific signs, symptoms, or findings prompting focal evaluation [3].

Growth Velocity

Growth velocity is often more informative than a single percentile measurement. Height deviating more than two major percentile lines relative to peers is abnormal [5].

Normal height velocity by age:

Measure every 3 to 6 months in children older than 6 months. Shorter intervals may be appropriate in younger children or specific clinical situations.

Open the Growth Velocity Calculator →

Clinical pearl. A child growing at a steady 5 cm/year and tracking the 10th percentile is a normal genetic variant. A child previously growing at 8 cm/year who decelerates to 3 cm/year is a significant finding, even while still at the 25th percentile. The deceleration is the red flag, not the percentile position.

Interpreting the pattern:

• Weight velocity declines with preserved height velocity: consider inadequate intake or malabsorption.
• Height velocity declines: consider systemic illness or an endocrine disorder.

Preterm Infants: Age Correction

Corrected age = Chronologic age − (40 weeks − Gestational age at birth)

A 2025 study of extremely (<28 weeks) and very (28 to <32 weeks) preterm infants found that using chronologic age instead of corrected age misclassified up to 72.9% as stunted and 89.8% as underweight at term-equivalent age. Age correction is required for all growth measures through 36 months corrected age in these groups [4].

Chart selection by postmenstrual/corrected age [11]:

The INTERGROWTH-21st Preterm Postnatal Growth Standards are an alternative. These curves overlap with the WHO Child Growth Standards by 64 weeks postmenstrual age (6 months corrected age), without requiring further adjustment [12,13].

Caution. Using chronologic instead of corrected age in an extremely or very preterm infant can generate a false impression of faltering weight for up to 36 months. Confirm which age is plotted before acting on a chart position.

Syndrome-Specific Growth Charts

Standard charts can incorrectly suggest pathology in children whose genetic condition confers a different growth potential. Use condition-specific charts alongside standard charts to catch a growth problem superimposed on the underlying condition.

Open the Down Syndrome Growth Calculator → Open the Turner Syndrome Growth Calculator →

Percentile Crossing in Infancy

In the first 6-12 months, normal infants frequently cross percentiles while regressing toward genetic growth potential. Children born with anthropometric z-scores greater than 0 (>50th percentile) are more likely to show z-score declines during the first 2 years of life.

Clinical pearl. An infant born large due to maternal diabetes may track the 95th percentile at birth and settle to the 50th percentile by 6 months. This is physiologic and does not, by itself, meet faltering weight criteria.

Findings that warrant concern:

• Persistent downward crossing of percentiles
• Large percentile drops (e.g., 75th to 10th percentile in 3 months)
• Declining height velocity
• Weight-for-length or BMI z-score less than −1.65
• Decline in z-score ≥1.0

Midparental Height and Bone Age

Sex-adjusted midparental height:

• Boys: (Mother's height + Father's height + 13 cm) / 2
• Girls: (Mother's height + Father's height − 13 cm) / 2 [5,14]

Compare the child's predicted adult height (projected from the current growth curve percentile) with midparental height to help distinguish normal variants from pathologic stature [5,14].

Bone age versus chronologic age [5,14]:

Management

1. Select the appropriate chart: WHO for children under 2 years, CDC for 2 years and older, Fenton for preterm infants, syndrome-specific charts for genetic conditions [1,2,6,8,11].
2. Use z-scores for precise assessment, particularly at the extremes of the growth curve or when tracking treatment response [3].
3. Correct for prematurity through at least 24 months corrected age; extend to 36 months for extremely and very preterm infants [4].
4. Track growth velocity with measurements every 3-6 months in children older than 6 months [5].
5. Calculate midparental height to establish genetic growth potential and compare with predicted adult height [5,14].
6. Recognize physiologic percentile crossing in

References

1. Grummer-Strawn LM, Reinold C, Krebs NF. Use of World Health Organization and CDC growth charts for children aged 0-59 months in the United States. CDC (2010).
2. Grummer-Strawn LM, Reinold C, Krebs NF. Use of World Health Organization and CDC Growth Charts for Children Aged 0-59 Months in the United States. MMWR Recomm Rep. 2010;59(RR-9):1-15.
3. Kersten HB, Goday PS, Abdelhadi R, et al. Clinical Practice Guideline for Diagnosis and Management of Faltering Weight. Pediatrics. 2026;e2025075764.
4. Elmrayed S, Dai S, Lodha A, Kumar M, Fenton TR. Preterm Growth Assessment: The Latest Findings on Age Correction. J Perinatol. 2025;45(5):607-615.
5. Caro R, Savel P, Moss PI. Evaluation of Short and Tall Stature in Children. Am Fam Physician. 2025;111(6):532-542.
6. Zemel BS, Pipan M, Stallings VA, et al. Growth Charts for Children With Down Syndrome in the United States. Pediatrics. 2015;136(5):e1204-1211.
7. Cattoni A, Molinari S, Cali L, et al. TRISOMY 21: Development of Syndrome-Specific Growth Charts From a Wide Italian Cohort and Validation of BMI as a Predictor of Increased Risk of Metabolic Derangement. J Endocrinol Invest. 2026;49(4):931-946.
8. Hoover-Fong J, Scott CI, Jones MC. Health Supervision for People With Achondroplasia. Pediatrics. 2020;145(6):e20201010.
9. Neumeyer L, Merker A, Hagenas L. Clinical Charts for Surveillance of Growth and Body Proportion Development in Achondroplasia and Examples of Their Use. Am J Med Genet A. 2021;185(2):401-412.
10. Daymont C, Hwang W, Paul IM, Shur N, Freedman DS. Creation and Evaluation of New Growth Charts With a Gradual Transition From WHO to CDC Values. Pediatrics. 2025;e2025070697.
11. Bybel M, Delaney CA, Coble K. Outpatient Care of the Premature Infant. Am Fam Physician. 2025;112(2):153-161.
12. Villar J, Giuliani F, Barros F, et al. Monitoring the Postnatal Growth of Preterm Infants: A Paradigm Change. Pediatrics. 2018;141(2):e20172467.
13. Villar J, Giuliani F, Bhutta ZA, et al. Postnatal Growth Standards for Preterm Infants: The Preterm Postnatal Follow-Up Study of the INTERGROWTH-21st Project. Lancet Glob Health. 2015;3(11):e681-691.
14. Allen DB, Cuttler L. Short Stature in Childhood - Challenges and Choices. N Engl J Med. 2013;368(13):1220-1228.