Growth charts: your baby's line tells a story

Start by reading the axes

Before following a line, check what the chart represents. The horizontal axis usually shows age; the vertical axis shows the selected measurement and its unit. A weight-for-age chart answers a different question from a height chart, even when both are drawn with similar-looking curves.

Check that the birth date and measurement date are correct. A weight taken six weeks ago belongs at your baby's age six weeks ago, not at today's age. An incorrect date can move a correctly entered measurement to a misleading place on the chart.

What a percentile actually means

A percentile describes where a measurement sits compared with the reference group at the same age and sex. Around the 50th percentile, roughly half the reference measurements are lower and half are higher. It does not mean a baby is ‘50 per cent grown’ or has achieved half of a goal.

The middle curve is not a target every baby should move towards. A clinician considers the child's history and pattern, not only which printed curve is nearest. Avoid changing feeding or care just to make a point move towards a preferred percentile.

Further guidance: Pregnancy, Birth and Baby: Understanding baby growth charts

Tell the baby's data from the reference

In Baby Tracker, your baby's saved measurements use a solid, bright pink line and filled markers. The dashed lines are the bundled WHO reference curves. A dashed reference curve is not a prediction of the path your baby must follow next.

The website's growth tool shows one measurement against published reference bands. It does not store a personal growth history or calculate an exact percentile between the published bands. For example, a result between two reference lines is a range, not a precise diagnosis or a ranking to optimise.

Know which reference is being used

WHO publishes standards for several growth measures, including weight, length or height and head circumference. Baby Tracker bundles selected WHO tables locally. Child details are not sent to a reference-chart service to draw the comparison.

Your child's official health record or clinic may use a different chart for a particular age or situation. A difference between two displays is a reason to check the reference, dates and units with the professional involved. It is not a reason to overwrite a documented clinic measurement to make the screens agree.

Further guidance: WHO Child Growth Standards

Give each point its context

Write down where a measurement came from and how it was taken if that will help later. A clinic weight, a home scale reading and a measurement taken with clothing can have different context. The app cannot recover that information from the number alone.

Do not silently convert a lying-down length into a standing height or adjust age for prematurity yourself to match a chart. The browser tool uses calendar age without a prematurity correction. Bring those circumstances to your healthcare team so the appropriate assessment is used.

Use a trend to start a conversation

A series of dated points is easier to discuss than a remembered number. Ask your child health nurse or doctor to explain a change you do not understand, and bring the original records if one reading seems out of place. Check for an input mistake before assuming the baby changed abruptly.

You might ask which reference they use, whether the measurement method matters and when another measurement is appropriate. Keep routine checks and your baby's wellbeing at the centre of the conversation. A graph is there to make the history clearer, not to turn growth into a competition.