As the name suggests, baby or infant growth charts indicate how your child is growing. It’s important not to compare your baby’s size with that of other babies since this may be misleading. The most important thing is that your baby is healthy, happy and growing appropriately.
What is an infant growth chart?
An infant growth chart helps you, your doctor and other health professionals keep track of how your baby is growing. There are different charts for boys and girls, for infants and for older children.
Growth charts record changes in your baby’s length, weight and head circumference. These measurements are marked down on the chart so you can see how they change over time. On the vertical (up-and-down) axis is the measurement; on the horizontal (side-to-side) axis is the baby’s age.
There will probably be a growth chart in your child’s personal health record (often called the blue, red or green book, depending on which state you live in). Your child and family health nurse or GP may also keep a birth chart for your baby.
All babies grow at different rates, and ‘normal’ growth ranges a lot. As long as your baby continues to grow, is responsive and is healthy, there’s usually no need to worry about the trend on the growth chart.
How to understand percentiles
Infant growth charts are usually calculated using the World Health Organization’s (WHO’s) growth standards. These show normal growth in babies for the first 5 years. Infant growth charts allow health professionals to compare your baby’s growth with that of all other babies of the same age.
Like adults, babies come in all shapes and sizes. The growth charts show this by using ‘percentiles’. A baby on the 50thpercentile for weight, for example, is right in the middle of the normal range: 50% of babies their age are lighter, and 50% are heavier. A baby on the 5th percentile weighs less than 95% of other babies of that age. A baby on the 90th percentile weights more than 90% of other babies that age.
Some babies will always be small and others will always be large. The important thing is that they are growing as expected for their percentile. The charts help you track this by showing normal growth curves (i.e. always increasing). You can plot your baby’s growth to see if it follows a similar pattern to other babies on that percentile.
How will my baby be measured?
Your baby will be weighed and measured at birth. After that, repeating the measurements once a month or so is usually enough to track how they are growing. Don’t worry if their weight goes up and down from day to day – this is normal.
Babies under 2 years old are usually weighed on a special infant scale (newborns will lie down on the scale). It’s more accurate to weigh babies with no clothes on until they are 12 months. After they turn 2, they can be measured standing up in light clothes. You baby’s head circumference will be measured using a tape measure.
If your child was born prematurely, their age needs to be corrected on the chart until they turn 2 years old.
Growth charts can actually be used until your child turns 18. Your child and family health nurse or GP can tell you what other health checks are needed to make sure your child is growing and developing normally.
When should I be worried?
Parents are often worried that their baby isn’t growing fast enough. However, while it’s important to measure a child’s growth to see if they are healthy and developing properly, it’s not the only way to tell if they’re healthy.
All babies lose some weight in the week after birth. Most babies double their birth weight by 4 months and triple it by 13 months (for boys) or 15 months (for girls).
There is unlikely to be anything wrong if your baby:
- has at least 5 very wet nappies each day
- does well-sized, soft poos
- has good skin colour and muscle tone
- is meeting other developmental milestones
Weight gain can be affected by an infection or vomiting. If you are ever worried, talk to your child and family health nurse or GP.
If your child’s percentile changes significantly – for example, if they drop by 2 percentile lines – then talk to your child and family health nurse or GP. They will assess the child’s growth trend to see if there is any reason to be worried.
Remember, don’t compare your child’s growth to that of other kids. The important thing is that they continue growing following the same percentile.