What Is a Growth Chart?
A growth chart is used to plot a child's measurements and compare them with children of the same age and sex. Growth charts help the healthcare team follow a child's growth pattern over time. A single percentile does not diagnose a problem—the pattern across multiple visits is important.
Which Growth Chart Do We Use?
| Age | Chart | Common Measurements |
|---|
| Birth to <2 years | WHO — World Health Organization Growth Standards | Weight-for-age, length-for-age, weight-for-length, and head circumference-for-age |
| 2 years and older | CDC — Centers for Disease Control and Prevention Growth Charts | Weight-for-age, stature-for-age, and BMI-for-age as appropriate |
Remember: For children younger than 2, use weight-for-length rather than BMI-for-age for routine growth assessment. At age 2, the child transitions from WHO to CDC charts.
What Does “Percentile” Mean?
A percentile shows where a child's measurement falls compared with the reference population of children of the same age and sex.
| Example | How to Explain It |
|---|
| 50th percentile | The child's measurement equals or exceeds about 50% of the reference population of the same age and sex. |
| 75th percentile | The child's measurement equals or exceeds about 75% of the reference population of the same age and sex. |
| 10th percentile | The child's measurement equals or exceeds about 10% of the reference population of the same age and sex. |
Key concept: The 90th percentile does not mean the child is “90% healthy,” nor does the 10th percentile automatically mean something is wrong.
How to Plot a Measurement
- Choose the correct chart for the child's age and sex.
- Make sure the child's age and measurements are accurate.
- Find the child's age along the horizontal (X) axis.
- Find the measurement—weight, length/height, head circumference, or BMI—on the vertical (Y) axis.
- Follow both points until they intersect and place a dot at the intersection.
- Identify the percentile curve closest to the plotted point.
- Compare the point with measurements from previous visits to look at the child's growth trend.
Birth to <2 Years — WHO (World Health Organization) Charts
| Chart | What It Helps Assess |
|---|
| Weight-for-age | Weight compared with age |
| Length-for-age | Recumbent length compared with age |
| Weight-for-length | Weight in relation to the infant's length |
| Head circumference-for-age | Head growth compared with age |
WHO outer cutoffs: The WHO charts use the 2nd and 98th percentiles as important outer cutoff values. Measurements outside these ranges require appropriate clinical assessment—not a diagnosis by the MA.
Ages 2–20 — CDC (Centers for Disease Control and Prevention) / BMI-for-Age
Children are still growing, so their BMI is interpreted by age and sex. Do not use adult BMI categories for pediatric patients.
| BMI-for-Age Percentile | Category |
|---|
| < 5th percentile | Underweight |
| 5th to < 85th percentile | Healthy weight |
| 85th to < 95th percentile | Overweight |
| ≥ 95th percentile | Obesity |
What Should the Medical Assistant Remember?
- Measure accurately. Incorrect height, weight, length, or head circumference can place the child on the wrong percentile.
- Use the correct chart. Check age and sex before plotting.
- Plot accurately. Double-check the age and measurement before placing the point.
- Look at the trend. Growth over time is more informative than one isolated measurement.
- Do not diagnose. Document the measurement and percentile and report concerning findings or major changes according to office policy.
MA charting example: “Weight 32.0 lb; height 38.5 in. Measurements plotted on age- and sex-appropriate growth chart. Provider notified of significant change from previous growth pattern.”