WHAT NHS GUIDANCE SAYS

Follow the curve,
not the number.

Every baby draws their own line.

The curved lines in the red book are centile lines, built from measurements of many healthy children. What matters is the pattern over time: a baby on a low line can be growing just as well as one near the top.

THE PATTERN matters more than one weigh-in

Read a curve

A baby's tiny bare feet resting on a soft cream blanket beside a coiled cloth measuring tape — AI-generated image, not a photograph of a real person or place.

Some early weight loss is normal
One line up or down is common
Crossing two lines: ask
Growth charts, made simple

THE SHORT ANSWER

Babies follow curves,
not straight lines.

A growth chart is read over weeks and months.
Three things the guidance wants parents to know.

FIRST WEEKS

A small dip is normal

It is normal for babies to lose some weight in the first few days. The NHS says most babies are at, or above, their birthweight by 3 weeks.

See the numbers

CENTILE LINES

Any line can be healthy

Centile lines show how a child compares with others of the same age and sex. RCPCH says weights and heights anywhere within the centile lines are considered normal.

Read a curve

THE PATTERN

Watch for big crossings

Measurements may go up or down by one centile line, but crossing two is less common. If that happens, the NHS says talk to a health visitor.

What to do

General information only, not professional safety advice. If someone is in immediate danger, call the emergency services.

A QUICK CURVE CHECK

What is the
chart showing?

Pick a pattern you might see in the red book. The bar shows how strongly the guidance points to talking to a midwife, health visitor or GP.

Curve check

Choose a patternRoughly following one lineUp or down by one lineCrossing two linesLost 10% or more early onNot back to birthweight by 3 weeks

Roughly following one lineUsual pattern

Weights and heights anywhere within the centile lines are considered normal. A baby on a low line can be growing perfectly well.

Up or down by one lineCommon

The NHS says measurements may go up or down by one centile line. Weight can also dip during an illness and usually recovers within 2 to 3 weeks.

Crossing two linesTalk to a health visitor

It is less common for babies to cross two centile lines. If it happens, the NHS says talk to a health visitor, who can advise you.

Lost 10% or more early onCheck and feeding review

RCPCH says that if a baby loses 10% or more of their weight in the first two weeks, they should be examined and their feeding reviewed.

Not back to birthweight by 3 weeksGet support

A midwife or health visitor will support you if your baby has not regained their birthweight by 3 weeks, including talking about feeding.

Sources: NHS, Your baby's weight and height; RCPCH, Growth charts for parents and carers; NICE guideline NG75, Faltering growth (2017).

Based on NHS, RCPCH and NICE guideline NG75. This is general information, not personal medical advice.

TWO NUMBERS WORTH KNOWING

The curves come
from real children.

One figure on the first weeks of life,
one on the study behind the chart.

3 weeks

When most babies are back to birthweight

It is normal to lose some weight in the first few days. NICE says the loss usually stops after about 3 or 4 days, and most babies have regained their birthweight by 3 weeks.

BIRTHWEIGHT · NHS

≈ 8,500

Children measured to draw the curves

The WHO Multicentre Growth Reference Study collected growth data from about 8,500 children in Brazil, Ghana, India, Norway, Oman and the USA between 1997 and 2003.

THE STANDARD · WHO

The UK-WHO charts are based on the WHO Child Growth Standards for healthy breastfed babies, but RCPCH says they should be used for all babies, however they are fed.

FOUR THINGS TO KNOW

Weigh less often,
read the trend.

Frequent weighing can make normal ups and downs look like a problem. The NHS suggests a simple rhythm after the first two weeks.

Weigh in the first 2 weeks
Your baby will be weighed during the first 2 weeks to check they are regaining their birthweight.
Then no more than monthly
Up to 6 months, no more than once a month; from 6 to 12 months, every 2 months; over 1, every 3 months, unless there are concerns.
Keep the red book up to date
Growth is plotted in the personal child health record, the red book. Take it to reviews and appointments.
Ask if a line is crossed
If weight crosses two centile lines, or you are worried, talk to a health visitor or GP.

A parent's hands resting on a closed plain red booklet with a pencil beside it on a wooden table next to a cup of tea — AI-generated image, not a photograph of a real person or place.

An empty set of baby weighing scales in a bright clinic room, a folded white blanket on the curved tray — AI-generated image, not a photograph of a real person or place.

WHY THERE IS A GAP

No lines for
the first two weeks.

The UK-WHO charts have no centile lines between birth and two weeks. RCPCH explains that babies have very individual weight patterns at this age, so they are weighed instead and checked if they lose 10% or more.

Boys and girls have separate charts because boys tend to be a little heavier and taller. It is also normal for a baby to sit on different centiles for weight and length, though the two are usually fairly similar.

Questions

Questions people ask

What does it mean if my baby is on the 9th centile?

Centile lines show how a child compares with others of the same age and sex. RCPCH says weights and heights anywhere within the centile lines are considered normal; the pattern over time matters most.

Is it normal for a newborn to lose weight?

Yes. The NHS says it is normal to lose some weight in the first few days, and most babies are at, or above, their birthweight by 3 weeks.

How often should my baby be weighed?

After the first 2 weeks, the NHS suggests no more than once a month up to 6 months, every 2 months from 6 to 12 months and every 3 months over 1, unless there are concerns.

Why do the charts start at two weeks?

There are no centile lines between birth and two weeks because babies have very individual weight patterns then. They should still be weighed, and checked if they lose 10% or more.

Are the charts only for breastfed babies?

They are based on healthy breastfed babies, but RCPCH says they should be used for all babies however they are fed, and for children from all ethnic backgrounds.

Follow the curve,
not the number.