Baby growth charts: how to read them without worrying

At every check-up, baby is weighed, measured, and a new dot joins their chart. For many parents, that little dot triggers a question: is this normal? Here's how to read these charts with a little more peace of mind.

What a growth chart shows

A growth chart compares your child's measurements with those of a very large number of children of the same age and sex. The most widely used charts in the world are from the World Health Organization (WHO), built from healthy children followed in several countries. Depending on the country, the health record may also use national charts.

Three measurements are usually tracked: weight, length (or height, once measured standing) and head circumference.

Percentiles: P3, P50, P97

The lines on the chart are percentiles. If your child is on the 50th percentile (P50), half of children their age are lighter and the other half heavier. If they're on the P25, 25% of children their age weigh less than they do.

The area between P3 and P97 includes the vast majority of healthy children. Being on the P10 isn't "worse" than being on the P75: smaller parents often have a smaller child, and that's perfectly normal.

The trend matters more than a single dot

A single measurement says very little. A baby weighed right after a feed, or with a full diaper, won't show the same number as an hour later. Pediatricians mainly look at the shape of the curve over time: is it rising steadily, roughly parallel to the reference lines?

In the first days, some weight loss is usual before baby gets back to their birth weight. After that, the curve generally settles into a channel.

When to talk to your doctor

Some signs are worth raising with your pediatrician or doctor, without waiting for the next visit if you're worried:

• the curve stays flat over several measurements, or drops;
• it clearly crosses several percentile lines, up or down;
• measurements fall outside the P3–P97 range;
• you also notice other signs: baby feeds little, has fewer wet diapers, seems very tired.

In the vast majority of cases there's a simple explanation. But it's the health professional's role to assess it, by examining your child.

A few practical tips

• Note each measurement with its date, ideally those taken at the doctor's, which are the most reliable.
• Weigh baby in comparable conditions each time.
• Keep all measurements in one place, so both parents have the same information.

In Nivellia, each measurement is automatically plotted on the WHO reference charts, with the average weekly weight gain calculated right on your phone. You can also export everything as a PDF to show your pediatrician.

This article is for information only and does not replace advice from a health professional. If you have any doubt about your child's health, consult your doctor or pediatrician.