Baby weight and growth charts explained

Your baby's growth chart - how it works

Growth charts plot a baby's weight against height on lines called centiles.

The lines represent a zone, or range of measurements, within which your baby is expected to grow normally.

If she's on the top line, or centile, it doesn't mean she's overweight. And she's not underweight if she's on the lower line.

Regardless of which centile she's on, as long as she continues to follow it roughly then she's gaining weight as she should be.

"Keeping a chart gives mums the confidence that they’re doing things right, and it makes it easy for health visitors to spot whether a baby is gaining too much or not enough weight,” explains Sam Saunders.

“The growth charts are based on measurements from exclusively breastfed babies so mums who bottlefeed may find their baby is heavier than average,” adds Sam.

What's normal for a newborn baby's weight?

To begin with you may notice your baby’s weight drop, but don’t panic as this is completely natural. “It takes a while for a newborn to get used to drinking milk rather than getting food through the placenta,” says independent midwife Joy Horner. Which means she can lose up to 15% of her birth weight in the days following birth, but ideally at 2 weeks you want her weight back to where she started from.

How much weight gain is normal?

Once things have settled down, an average-sized baby should gain between half an ounce and an ounce per day, and by 6 weeks, should have doubled her weight. “But it isn’t an exact science as she may have spurts or slower periods of growth, which is normal, and it’s OK if she puts on more weight one week and less the next,” says independent midwife Joy Horner.

Be prepared for blips, too, as weight may fluctuate when your baby starts getting active, during teething or when she’s being moved onto solids.

When your baby will be weighed

“Your baby is weighed at birth, and normally, again at five days and 10 days by your midwife,” says community nursery nurse Sam. “Your health visitor then usually takes over and will weigh again at 14 days and from then on it’ll be every fortnight up to 6 months, and every month up to a year, but these times may vary slightly from clinic to clinic.”

The results from her weigh-ins are plotted on a growth chart in her health record book.

Why you can't just weigh your baby yourself

You might be thinking, ‘Why all the fuss? Why can’t I just weigh my baby on scales at home?’

“That’s not really such a good idea,” advises Sam. “This is because the scales you have at home aren’t regularly serviced like they are in clinics, so you can’t be sure they’re accurate, plus it needs to be done by a trained health professional.”

Your big baby - will she stay big?

“If your baby was born big she’s likely to be heavier than average just because she’s started off heavier, but as long as her weight gain is at a healthy rate your health visitor won’t be worried,” says Sam. “If she moves out of her centile to become heavier, your health visitor will ask how often and how much your baby is feeding, how many wet and dirty nappies she has and whether she’s settling and sleeping well.”

If that’s all normal she’ll generally then refer her to a GP, who may organise for her to see a paediatrician who’ll look into slowing her weight gain down as opposed to getting her to lose excess pounds.

Your underweight baby's growth

“As long as her weight remains within the weight line she started on, your baby is gaining weight at an acceptable rate,” says Sam. “But if her weight drops below the centile she started on, your health visitor will do the same checks as if she was overweight and then decide whether or not it’s necessary to refer her to a GP.”

Your premature baby's growth

Premature babies are usually born underweight and might not put on weight at the same rate as a full-term baby for as long as two years. “But the new-style charts have graphs for premature babies so they won’t be compared to full-term babies,” says Joy.

Premature babies normally have scheduled feeding, calculated by their weight, rather than being fed on demand. This is because they often won’t wake up to feed. Managing their feeds like this also means health professionals can monitor their food intake more carefully. “Some premature babies may be given a special premature baby milk to help them gain weight,” says Sam.

Multiple births - how twin babies are weighed

Twins are usually born at different weights and have different appetites, so are treated differently. “Each will have his own weight chart and grow at his own pace,” says Joy.