Growth charts and Anthropometry

Growth charts are essential surveillance tools in pediatric practice that represent the frequency distribution curves (percentiles or z-scores) of anthropometric parameters in a reference population.
Plotting a single value determines if a child is within the normal range at a specific point in time, while sequential plotting allows monitoring of growth trends and trajectories against the median.
Growth parameters are highly sensitive indicators of overall well-being, chronic disease status, nutritional adequacy, and psychosocial stress.

Types of Growth Standards and References

The selection of appropriate growth charts depends on the age of the child and the clinical context.
It is critical to distinguish between a "growth standard" (which prescribes how children should optimally grow) and a "growth reference" (which describes how a specific population actually grew),.

Feature	WHO Multicentre Growth Reference Study (MGRS) Charts	CDC 2000 Growth Charts	Indian Academy of Pediatrics (IAP) Charts
Age Range	0 to 5 years (routinely recommended for 0-24 months),.	2 to 19 years.	5 to 18 years,.
Data Nature	Growth standard (prescriptive, describing optimal growth),.	Growth reference (descriptive, based on historical cross-sectional data),.	Growth reference based on contemporary data from 33,148 Indian children.
Population Base	Multi-country data including Brazil, Ghana, India, Norway, Oman, and the USA.	United States specific data (NHANES).	General Indian pediatric population.
Feeding Norm	Establishes the exclusively breastfed infant as the biological normative growth model.	Includes an overrepresentation of formula-fed infants.	Consolidates WHO-MGRS and Indian reference data to suit local demographics.

For infants and toddlers (under 2 years), routine parameters plotted include weight for age, length for age, head circumference for age, and weight for length,.
For children older than 5 years, height for age and Body Mass Index (BMI) for age are the most important parameters for defining normal or abnormal growth and nutritional status.
BMI is calculated as weight in kilograms divided by the square of height in meters, and it must be interpreted strictly relative to age and gender,,.
The normal BMI trajectory is characterized by a relatively flat curve between 2 and 5 years of age, making age-specific plotting crucial for accurate interpretation,.

Percentiles define the percentage of individuals in a population who have achieved a specific measured quantity (e.g., the 5th, 10th, and 25th percentiles correspond to -1.65, -1.3, and -0.7 standard deviations, respectively).
Z-scores allow for cross-population standardization and are calculated using the formula: Z-score = (Observed value - mean value) / Standard deviation.

Z-Score / Percentile	Clinical Interpretation
Between -2.0 and +2.0 SDS (3rd to 97th percentile)	Represents the permissible range of variation for healthy individuals; normal growth,,.
< -2.0 SDS or < 3rd centile	Indicates stunting/short stature (if for height) or underweight/wasting (if for weight/BMI).
< -3.0 SDS	Indicates severe stunting, severe wasting, or severe underweight. Children in this category are highly likely to suffer from pathological short stature rather than physiological variants.
> +2.0 to +3.0 SDS (> 85th to 95th centile for BMI)	Corresponds to the threshold for overweight. In IAP charts, the 23rd adult equivalent centile (approx. 71st-75th centile) is used for defining overweight,,.
> +3.0 SDS (> 95th centile for BMI)	Indicates obesity,,.

Most healthy children will strictly maintain their established growth percentile over time.
Growth failure must be actively differentiated from static short stature. Growth failure is explicitly defined as a downward crossing of more than two percentile lines for height or an abnormally low height velocity for age and sex.
The following chart patterns serve as immediate red flags indicating a problem or risk of a problem:
- A child's growth curve crossing a major z-score line or two major centile lines.
- A sharp incline or decline in the child's growth curve.
- A growth curve that remains entirely flat or stagnant (e.g., an abnormal stagnation of weight highly suggestive of celiac disease, malnutrition, or recurrent infections),.
Poor linear growth accompanied by a decreasing BMI strongly suggests a nutritional or gastrointestinal etiology, whereas poor linear growth accompanied by a robust or increasing BMI typically points to endocrinological pathologies (e.g., hypothyroidism, growth hormone deficiency, or cortisol excess).

Growth charts vividly display specific patterns that aid the pediatric diagnostician in distinguishing the etiology of abnormal growth.

Etiology of Short Stature	Characteristic Growth Chart Trajectory
Familial Short Stature	The child's height is below the 3rd centile but appropriate for the genetic potential (mid-parental height). Growth runs parallel to and just below the 3rd centile throughout childhood, with normal height velocity and bone age equating to chronological age,,,.
Constitutional Growth Delay	Growth decelerates during the first year to fall below the 3rd centile, then resumes a normal velocity parallel to the norm. There is a downward deviation during the expected age of puberty, followed by a late growth spurt allowing the child to reach a normal adult target height,,,.
Pathological Short Stature (Postnatal Onset)	Height tracks normally initially, followed by a noticeable linear deceleration and a downward crossing of percentiles. Common in chronic systemic illness, severe undernutrition, or acquired endocrine failures,,.
Small for Gestational Age (SGA) without Catch-up	Born below the 10th centile for weight/length. Fails to exhibit the expected rapid upward crossing of percentiles (catch-up growth) during the first 12 to 24 months, remaining persistently below the 3rd centile,,.

Height velocity is the rate of vertical growth over a specified time, expressed as cm/year.
Plotting velocity accurately helps predict ultimate adult height and facilitates the early identification of subtle growth-retarding factors before gross stunting occurs,.
Average height velocity is approximately 25 cm/year in the first year, decelerates to 4-6 cm/year in prepubertal children (4 to 9 years of age), and peaks dramatically at 8-12 cm/year during the pubertal growth spurt,.

Correcting for Prematurity: The gestational duration of prematurity must be actively subtracted from the infant's chronological age. This correction is required for accurately plotting length, weight, and head circumference until two to three years of age to avoid the overdiagnosis of growth failure,,.
Target Height Estimation: Mid-parental height (MPH) must be calculated to estimate genetic potential. For boys: (Mother's height + Father's height + 13 cm) / 2. For girls: (Mother's height + Father's height - 13 cm) / 2. This target should be plotted at the 18-20 year mark on the chart to establish expected percentile tracking,.
Condition-Specific Charts: To prevent misclassification of growth abnormalities, specialized charts must be utilized for patients with inherent growth-altering conditions. Standardized specific charts exist for very low birthweight (VLBW) infants, Trisomy 21 (Down syndrome), Turner syndrome, and Achondroplasia.
Preterm Fetal-Infant Charts: For extremely premature neonates, specialized tools such as the Fenton growth chart (an update of the Babson and Benda chart) allow for plotting parameters starting from 22 weeks of gestation to smoothly track extrauterine transition,,.