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Dr Anna Maw
Consultant pediatrician at Cambridge University NHS Trust in the UK. A child doctor specializing in brain development and neurology. She has three children.
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Baby health

Your baby's/ toddler's weight and growth

A guide as to what is the optimal weight gain for your baby or toddler. What it means, and what you can do, if your child is gaining too much, or too little, weight. We describe what the weight charts mean, and what it means to 'track along a percentile. We also discuss what these charts mean for premature babies.
In Short

The weight charts in the UK NHS 'Little Red Book' are based on WHO growth charts for breastfed babies and they map your baby’s weight gain and weight compared to other babies of the same sex and age who are breastfed.

So if your baby girl’s weight at 1 month is in the 25th percentile, this means that if there were 100 1-month-old baby girls together in a room, 24 would weigh less than your baby and 75 would weigh more.

Your health visitor and GP will expect your baby to track along her centile. That is – born on the 25th percentile – roughly stay on the 25th percentile although a little movement up or down is normal.

If there is a big change – such as crossing more than 2 lines on the chart – your baby might be checked out by a paediatrician to find out if there is an underlying medical problem or feeding problem.

The video above explains how small your baby’s stomach is at first and how frequent feeds are necessary to fill up and refill their tiny stomach.

How are the growth and weight measurements taken?

Your child is measured very carefully using three different methods:

The doctor or nurse places your naked baby on a scale (either a traditional beam scale or an electronic model). Weight is measured in pounds to the closest ounce or in kilograms to the nearest tenth of a kilo.

Length (height)
The doctor or nurse measures your baby, lying down, from the top of her head to the bottom of her heel. Some doctors use a special device with a headboard and a movable footboard for more accurate results.

Head circumference
The doctor or nurse places a flexible measuring tape where your baby’s head has the largest circumference – just above the eyebrows and ears, and around the back of the head where it slopes up prominently from the neck.

The size of your baby’s head matters because the size of her skull reflects the growth of her brain.

So if a baby’s brain isn’t growing and developing normally, her head circumference may not be increasing as it should. On the other hand, if the skull grows too quickly, it could be a sign of a problem like hydrocephalus (the buildup of fluid in the brain). Both conditions are unlikely, but important to rule out.

Premature babies

In the UK, you will be given a Personal Child Health Record, or ‘red book’, which has growth charts to help plot your baby’s growth and compare it with the average growth for their age. Babies born at less than 32 weeks are plotted in the low-birthweight chart. Babies born at 32-37 weeks are plotted in the preterm chart until two weeks after their estimated due date and from then on are plotted in the main charts, but with their gestationally corrected age.

If your baby is born prematurely, their milestones will be assessed from the time of their due date, not from when they were actually born. For example, if your baby was born 4 weeks early, her numbers are compared with full-term babies who are 4 weeks younger than her. By the age of two, their development will often even out with their peers, and you can use their actual birth date instead. In very premature babies, sometimes this is extended to three years of age.

As a new parent, there can seem to be a lot of focus on your baby’s weight. Your baby will be weighed at birth then you will be given your baby’s Little Red Book which also allows you to chart your baby’s weight gain over their first days, weeks, months and years.

If your baby is born with a low birth weight, underlying health problem, premature or with feeding issues your baby will have their weight assessed more frequently than the drop in well-baby clinics.

Can babies put on too much weight?

Babies are supposed to put on a lot of weight and have good fat deposits as they are growing at a faster rate than they ever will for the rest of their lives.

Interestingly a lot of new research looking at the effects of high rates of weight gain and baby weight are now reporting that very big babies and babies that have a high rate of weight gain may actually face greater long-term health problems than babies that put on an average amount of weight.

These can include hypertension and diabetes in adulthood and so now the medical profession is looking at optimum weight gain, which we see in breastfed babies that are feeding well and who are weaned and are encouraged to try lots of self-feeding, not just spoon feeding. who are mainly spoon fed should be fed responsively without being encouraged to finish portions when they appear reluctant in order to help them establish appetite control.

Optimal weight gain

What seems to be important is that babies’ feeding cues (signals of hunger and fullness) are respected as they feed and grow. Breastfed babies naturally develop appetite control and cannot be force fed. Bottle-fed babies should not be ‘forced’ to finish a bottle of milk, so instead, parents are led by their baby’s signals rather than the number of millilitres left in their bottle. This sensitive feeding style is also encouraged when solid food is started as the medical profession are beginning to see more and more very young children who are already obese. If you are concerned about your baby’s weight, weight gain or feeding behaviour you can speak to your GP or health visitor and raise your concerns.

Weight charts

Since 2009, the UK Red Book weight charts are based on breastfed boy babies and girl babies from around the world (in the past doctors may have used growth charts based on white babies and included formula fed babies who do not always put on weight in the optimal pattern observed in breastfed babies who are feeding successfully).

The weight charts map your baby’s weight gain and weight compared to other babies of the same sex and age.

The baby weights are then shown in percentiles so you can see how your baby’s weight compares to his or her peers. If you baby girl’s weight at 1 month is in the 25th percentile, this means that if there were 100 1-month-old baby girls together in a room, 24 would weigh less than your baby and 75 would weigh more.

Your health visitor and GP will also be interested to see if your baby tracks along their centile. So, generally, if your baby is born on the 25th centile, you would hope to see them always stay around that level (accepting for growth spurts and little dips) over their first year.

If your baby does see a big consistent fall in their growth centile your baby may be referred to a paediatrician or if there is a feeding problem they may be assessed by an infant feeding expert to check that there are no medical or anatomical (e.g. tongue tie) problems or underlying health problems that might be associated with low weight gain. They may use the term ‘faltering growth’ which can be an upsetting phrase to hear but it is not a reflection on you as a parent. If there is a problem, your baby will be helped with their feeding or underlying problem and hopefully will start to put on weight again and return to their natural centile.

Initial weight loss

Note that it is normal and expected that newborns will lose some weight in the first 5-7 days of life. A 5% weight loss is considered normal for a formula-fed newborn. A 7-10% loss is considered normal for breastfed babies. Most babies should regain this lost weight by day 10-14.

For more information, please click here to visit the Growth Foundation website.

Share the knowledge
This article is for information only and should not be used for the diagnosis or treatment of medical conditions. Essential Parent has used all reasonable care in compiling the information from leading experts and institutions but makes no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details click here.