How to read your child’s growth chart

A growth chart looks complicated, but it answers one simple question: is your child growing along their own path? The curved lines on the chart are centiles. If your child is on the 25th centile for height, it means that out of 100 children of the same age and sex, about 25 are shorter and 75 are taller.

There is no “good” line

Being on the 90th centile is not better than being on the 10th. A healthy child can sit anywhere on the chart. What matters is consistency: most children stay roughly on the same line year after year, because they are following their own inherited pattern.

What doctors look for

• Crossing downwards. A child who was on the 50th line and is now near the 10th has slowed down, and that change is worth explaining — even if the height still looks normal.
• Crossing upwards in weight while height stays flat. This pattern often prompts a check for hormone causes.
• A big gap between height and weight centiles. For example, weight far above height, or the reverse.
• Height far away from what the parents’ heights predict.

Points to remember about the first two years

Babies often shift between centiles in the first 18 months as they settle onto their own line, and breastfed and formula-fed babies grow with slightly different patterns. Crossing lines in this period is much less worrying than it is at six or eight years old.

Getting a useful chart

Measurements need to be taken the same way each time: no shoes, heels together, heels and back against the wall, eyes looking straight ahead. Weight in light clothing. Two or three good measurements a year, plotted with the date, are far more useful than many careless ones — and they are the single most valuable thing you can bring to a growth consultation.