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Information for Parents

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Why do we use growth charts?

The UK-WHO growth charts show how your child compares with other children of the same age and sex. They are drawn using measurements from many infants and children: from ages two weeks to 4 years, they use measurements of healthy breastfed babies collected by the World Health Organization (WHO) in six different countries. These charts show how healthy babies are expected to grow, whatever their ethnic origin and however they are fed.

At birth, and for babies born more than 3 weeks early, the charts use the birth weights of British infants and from age 4 to 20 years, measurements of British children collected in the 1980-90s. These charts show how children used to grow and gain weight when obesity was less common.

What do the charts show?

Children come in all shapes and sizes, so no two filled-in charts will look the same, but the chart helps us to check that your child is growing and developing as expected. Each centile line on the chart describes the number of children expected to be below that line, so half of all healthy children will be below the 50th centile, but only 9% below the 9th . Only one in a hundred children will be outside the two outer lines (0.4th and 99.6th centiles). As more measurements are collected and plotted, the chart also shows a child’s growth pattern.

When and how to weigh

Weigh babies and children up to 2 years of age without clothes or nappy, as this can make a big difference to the weight.

Be aware that different scales can give different readings, particularly if they are not electronic. If you notice this, try to take your baby/child to the same place for weighing each time.

Your baby should be weighed in the first week as part of the assessment of feeding. It is normal for a baby to lose weight in the first few days after birth. Most babies regain their birth weight by 3 weeks of age. Regaining weight after birth helps to show that your baby is healthy, and that feeding is going well.

After that, your baby will usually be weighed only when seen routinely, unless there is concern.

Some parents like to have their babies weighed often, but this can be misleading and cause unnecessary worry. For example, if one week your baby was weighed just after a big feed but the next week they were weighed before a feed, it could look as if they had not gained weight. Longer gaps between weights are more likely to show the true weight change. Your health visitor or doctor may recommend more frequent weights for children if there are concerns about slow weight gain or weight loss, but it is still important not to weight too often:

Age No concerns If there is slow weight gain or weight loss, no more often than:
Up to 3 months Age 5-10 days and at 8 and 12 weeks with immunisations Weekly
3-6 months Age 16 weeks with immunisations Fortnightly
6-12 months Age 1 year with immunisations Monthly
Over 12 months Every 6-8 weeks

Remember that if you want advice, you can always phone your health visitor or visit the clinic, without having your child weighed.

Measuring height and length

Up to the age of 2 years length, rather than height, is measured, lying down without shoes or nappy. Special equipment is needed for this, and it is difficult to measure length accurately, so this will not be done every time your child is seen. Usually, your Health Visitor or GP will only measure length if they are worried about your child’s growth or weight gain.

After 2 years of age, height is measured, standing up with shoes removed. It is important to measure height accurately, using proper measuring equipment. A tape measure or a book against the wall is not accurate enough. It is not usually necessary to measure height if your child is growing as expected. Once they go to school, in England, they will be measured with their classmates for the National Child Measurement Programme in their reception class and their last year in primary school.

Body mass index

From age 4 years, your child’s Body Mass Index (BMI) can be calculated from a measure of both weight and height. This measures how much weight your child is carrying, allowing for their height. It is calculated by dividing their weight (in kilograms) by their height (in metres), squared. The cut-off for a high BMI varies with age, but if a child’s BMI is above the cut-off, this generally suggests that they are overweight. A child with a low BMI is more likely to have a lean build rather than too little fat. Your GP or other health professional caring for your child will be able to discuss your child’s BMI with you.

The NHS has a website which can calculate Body Mass Index for children over 2 years of age.