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Information for Parents

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What do regular measurements tell us?

Weighing and measuring helps us to check that your child is growing and developing as expected.

Why do we use growth charts?

The lines on a growth chart are called centile lines and are based on measurements from many infants and children. They show the optimal range of weights, lengths and head circumferences for healthy children, and how one child compares with others of the same age and sex. For example, if your child’s weight is on the 25th centile, it means that if you lined up 100 children of the same age and sex in order of weight, your child would probably be number 25; 75 children would be heavier than your child, and 24 would be lighter. Weights, lengths and head circumferences that are anywhere within the centile lines on the chart are considered normal. Every child is different (they come in all shapes and sizes!), so no two filled-in charts will look the same. Even twins may have different growth patterns.

If a child’s growth pattern looks unusual, your health visitor or doctor may want to have a closer look to see why. This may involve taking more measurements or performing investigations. Most children who have such investigations are found to be perfectly normal; however, it is important to check an unusual pattern on the chart to make sure.

The UK-WHO growth charts

The UK-WHO growth charts are based on data:

  • From birth to age 4 years on measurements from healthy term babies (37 or more weeks gestation) collected by the World Health Organization (WHO) in six different countries. Healthy breastfed babies whose mothers did not smoke and who had access to good healthcare and nutrition were measured over time. The centile curves drawn using these measurements show how healthy babies are expected to grow, whatever their ethnic origin and whether breastfed or infant formula fed. For babies below 37 weeks gestation, measurements are plotted on growth charts based on the birthweights of British infants who were born prematurely.

  • From age 4 to 20 years on measurements from a large number of British children collected in the 1980-90s.

Weighing and measuring

Babies and children up to 2 years of age should be weighed without any clothes or nappy on, as this can make a big difference to the weight. Be aware that different scales sometimes 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.

Up to the age of 2 years your child is measured for length (i.e. lying down) rather than height. Special equipment is needed to measure length accurately and this will be recommended by a health care professional if needed. Your child should not be wearing a nappy when his/her length is measured.

After 2 years of age your child’s standing height should be measured. Your child’s shoes should be removed during the measurement. It is important to measure height accurately using a rigid rule with T piece or stadiometer.

From age 4 years, your child’s Body Mass Index (BMI) can be calculated from their weight and height measurements formula_BMI. BMI is a simple measure of fatness or thinness, and high levels suggest that the child may be carrying too much fat. The cut-offs for a high BMI in children are different from those used in adults and depend upon age. Some medical conditions or treatments that your child receives may mean that the BMI centile is not the best way to measure your child. A low BMI can be due to a relatively low amount of lean (muscle) tissue as well as fat. Your GP or other health professional caring for your child will be able to discuss your child’s BMI with you.

How often to weigh

It is normal for a baby to lose some weight in the first few days after birth. Your baby should be weighed in the first week as part of the assessment of feeding. Most babies get back to their birth weight by 2 weeks of age. This is a sign that feeding is going well and that your baby is healthy.

After that, your baby will usually be weighed only when seen routinely, unless there is concern. Weighing your baby too often can cause unnecessary concern; the list below shows how often, as a maximum, babies should be weighed to monitor their growth. However, most children will not need to be weighed as often as this. Many parents like to have their babies weighed more often. However, it is not always helpful and can cause unnecessary worry. For example, if one week your baby was weighed just after a big feed but the next week they were weighed after a long nap and 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. The recommended time between weighing is longer for older babies because they are growing more slowly. Your health visitor or doctor may recommend more frequent weighing for children if there are concerns about their growth or health or if they have certain medical conditions. If there are serious concerns about slow weight gain or even weight loss, a child could be weighed as often as:

  • daily if less than 1 month old
  • weekly between 1–6 months old
  • fortnightly between 6–12 months
  • monthly from 1 year of age

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

Beyond the age of two years children need only be weighed if there are worries about their health, growth or weight gain. Once they go to school, in England, they will be measured with their class mates for the National Child Measurement Programme in their reception class and their last year in primary school.

Frequently asked questions

I didn’t breastfeed or I stopped early – are these charts still right for my baby?

The charts show how breastfed babies grow if they are healthy and there are no problems. Babies grow most naturally when fed on breastmilk. If you use infant formula milk you want to know that your baby is still growing in the same healthy pattern that they would on breast milk. This chart helps you see if that is happening.

My baby was born prematurely. Is this taken into account?

If your baby was born early, weight and head circumference will be plotted on preterm charts until they are 2 weeks past your due date. This will help you and the health professionals tell how your baby is doing compared with other preterm babies. After this, weight and other measurements will be plotted on the main chart. Two centile values will be provided – one plotted at your baby’s actual age and the other at his/her ‘corrected’ age (taking into account the number of weeks your baby was born early).

How do I know my baby’s weight is OK in the first 2 weeks?

Weighing in the early days is important. Regaining weight after birth helps to show that your baby is healthy, and that feeding is going well. If your baby loses quite a lot of weight or is slow to regain their birth weight, this is a sign to look a little closer. If the weight loss seems a lot, your midwife or health visitor will calculate this as a percentage of their weight. If your baby has lost 10% or more (a tenth) of their birth weight, your midwife or health visitor will check how your baby is feeding. If you are breastfeeding or if you are giving infant formula milk, your midwife or health visitor will make suggestions about how you may help the baby feed more effectively to improve the weight gain and may recommend medical assessment. If any issues are identified a referral to specialist feeding services or a doctor may also be required.

If you make a change to how you feed your baby, it may take a little time for their weight to improve. Your midwife or health visitor may want to weigh them again to follow their progress.

My baby’s weight was on one centile and now it is nearly down to the next line – is this normal?

It is normal for the dots of your child’s weight to ‘wiggle’ up and down a bit, or to move gradually from being near one centile to the next one (up or down). It is less common for a child’s weight to cross two lines; if this happens your health visitor may want to keep a closer eye on your child for a while.

My child was ill and lost some weight, what should I do?

Children often lose some weight when they are not well. Once your child recovers from the illness, their weight should go back to the centile it was on before the illness within 2–3 weeks. If this does not happen, speak to your health visitor. The health visitor may measure your child’s length or height or investigate other issues.

When should length or height be measured?

For babies and children under 2 years, length rather than height is measured. This can be helpful if there is any concern about weight gain. However, it is quite difficult to measure length accurately, so this will not be done every time your child is seen. It is not usually necessary to measure length or height if your child is growing as expected.

My baby‘s head size has risen to the top of the centile chart – should I be worried?

British children have relatively large heads compared to the WHO standard, particularly after the age of 6 months, so it is fairly common for the head centile to be at the very top of the chart or even above it. This should only cause concern if the head centile goes on rising after the first few weeks or of there are other concerning signs or symptoms.