Understanding Your Baby’s Weight Chart

Newborn babies are weighed and measured regularly to check they are growing well and thriving. Weight is the variable most often used to measure growth or faltering growth in the UK. When breastfeeding is going well, a baby’s weight will roughly follow the shape of one of the pre-drawn curves (or centiles) on the weight-for-age charts in a baby’s personal development record (called ‘the red book’ in the UK). But what if a breastfed baby’s growth curve is much flatter or steeper than the lines on the chart?

This article

This article looks at what to expect in terms of normal growth for healthy, term babies; how to interpret your baby’s weight chart; when to be concerned about your baby’s weight, and when to take action. This is a companion article to Baby Not Gaining Weight and Is My Baby Getting Enough Milk?

Normal growth in the breastfed baby

In 2006 the World Health Organisation (WHO) published new growth standards that reflected the normal range of growth in healthy term breastfed babies across the world from non-smoking mothers. These are the charts that have been used in England since 2009 and replace charts that were previously based on growth in formula-fed babies. There are separate coloured charts for boys and girls because they grow at slightly different rates. Follow the links to see the WHO weight-for-age charts for 0-6 months (percentiles) for boys (blue) and girls (pink).

Normal loss and gain

The article Is My Baby Getting Enough Milk? reviews the losses and gains expected according to the WHO weight-for-age charts in the first few days of life:

The first two to four days
It is normal for a breastfed baby to lose a little weight before his mother’s milk comes in during the first two to four days of life and babies are well equipped for this. A loss of 5–7% weight is usually accepted as normal although more research is needed. If your baby has lost more than 5–7% of their bodyweight or is still not gaining weight after 2–4 days contact your breastfeeding specialist to review how breastfeeding is going.

After the first few days
Once your milk has come in, a weight gain of 30g–40g per day (or 7–10 ounces per week) in the first three months shows your baby is growing well 1. This slows down between 3–6 months to an average gain of 20g per day.

Regaining birth weight

It is commonly accepted that babies will be back to birthweight by two weeks of age 2. Macdonald et al 3 found that breastfed babies regained their birthweight by an average of 8.3 days of life.

Unexpected weight loss

A baby may have a higher than expected weight loss in the first few days if a mother had IV (intravenous) fluids during labour 4 5 6 7 or if breastfeeding is not going well. Monitoring your baby’s poop during this time can help with identifying milk intake; if milk is going in to your baby, lots of poop will be coming out (and be yellow by day five).

Later

Babies generally double their weight in the first four months and will have tripled their birth weight by the end of the first year (WHO growth standards, 2006).

What are centiles?

The lines marked as 3rd, 15th, 50th, 85th and 97th on the WHO charts are known as percentiles or centiles. Centiles divide the range of normal weights into 100 parts and are a useful measure of percentage in statistics. All healthy children will grow somewhere between the 1st and 100th centiles. For example:

  • If your baby is growing along the 3rd centile they are one of the smallest babies for their age. For every 100 babies only three weigh less than him or her (3%) and 97 weigh more (or 97%).
  • The 50th centile represents an average weight of all babies. Half of all healthy babies will be below this line, the other half will be above and one is not better than the other.
  • If your baby is growing along the 97th centile they are one of the largest babies for their age. For every 100 babies, 97 babies weigh less than him or her and only three (or 3%) weigh more.

Following centiles, normal growth

Growth patterns vary between babies and growth rarely follows a textbook curve. However, weight gain usually tracks within the space between two centiles 8, with periods of slower and faster growth. Despite fluctuations, the general direction of growth will follow the pre-drawn curves.

Above charts adapted from the WHO child growth standards chart, source: who.int/childgrowth/standards/weight_for_age/en/ accessed 20/09/2016

Crossing centiles

If a baby was born above the 50th centile, but later moves down to below the 15th centile, their growth curve would be described as having crossed two centiles (see baby B below). Crossing two or more centiles can be of concern because if a baby is not growing normally, his health could be at risk. Reasons for crossing centiles might include:

  • Baby not getting enough milk (the most common reason).
  • A medical problem or genetic syndrome.
  • Normal adjustment. Some babies who cross centiles may simply be adjusting from the nutritional conditions in the uterus to their genetic potential for growth 9. Perhaps their parents are both small and petite.

Faltering growth

If your baby’s growth continues to falter, their weight could eventually drop below the chart altogether and your baby’s health could be compromised. Stay in close contact with your health professionals and breastfeeding expert if your baby’s weight is crossing centiles and see the examples and ideas for action below.

So how is a doctor supposed to know which of the children who fall under the three percent curve are sick and which are healthy? Well that’s why the doctor went to medical school.

What are Z scores?

Z scores are another way to classify and compare data which you may see on some graphs. Z scores are explained in The Z-score or Standard Deviation Classification System (WHO).

Monitoring growth

Weight is generally used to measure growth but a baby’s length, and head or upper arm circumference may be measured too. Other signs that your baby is getting plenty of breast milk include your baby having plenty of wet and dirty nappies (diapers), your baby’s urine being pale coloured, and being contented between feeds—see Is My Baby Getting Enough Milk? for a summary.

How often to weigh your baby

Historically babies were weighed weekly in the UK. More recently, official advice in the UK has swayed towards weighing once a month between the ages of two weeks and six months, and less often after this time 10 11. While this frequency of weighing might be reasonable when breastfeeding is going well and a mother has good breastfeeding support, breastfeeding is not always established yet by two weeks after birth. If breastfeeding is not going well, leaving a newborn baby with poor or borderline weight gain for four weeks is too long both for baby’s health and for his mother’s potentially dwindling breastmilk supply.

Weigh weekly until breastfeeding is established

Until breastfeeding is well established, and you are reassured that your baby is easily gaining between 30g and 40g per day, weighing regularly will pick up any problems with weight gain early—so that help can be given to increase baby’s intake of breast milk. The sooner problems are addressed the better for your baby and your milk supply.

Plotting your baby’s weight

Your midwives and health visitors will record your baby’s weight in his personal development record (red book). The WHO chart in the red book shows the 0.4 centile and 99.6th centile. If you’re not sure whether the chart in your baby’s record is for breastfed babies you can plot your baby’s weight yourself by downloading the appropriate WHO chart (boys 0‑6 months and girls 0‑6 months).

Examples of growth faltering

The following scenarios are hypothetical and simplified, although they mirror real cases of poor growth associated with breastfeeding issues. Always consult with your health professionals if you have any concerns about your baby’s weight. Charts adapted from the WHO child growth standards: accessed 20/09/2016.

Growth faltering due to poor breastfeeding management

Sample growth chart with growth faltering
Slow weight gain for the first seven weeks (baby A)

In this example baby A’s weight faltered for nearly seven weeks. Her mother had been told to feed from one breast per feed every three to four hours (“to get to the hindmilk”) and her milk supply gradually dropped as a result. Simple changes such as increasing the frequency of feeds to every two hours or more, using both breasts per feed, using breast compressions and pumping will all help to increase milk supply. If mother’s milk supply responds quickly, formula supplements (or donor milk) will not be needed and in this example, baby A’s weight gain steadily improves once she gets more breast milk.

Growth faltering due to difficulty latching or poor tongue function

baby-growth-chart-baby-B-web
Crossing two centiles in the first six weeks (baby B)

In our second scenario baby B’s weight dropped two centiles during his first six weeks of life despite frequent feeding. Baby B might be very fussy and restless when feeding—often coming off the breast—or might fall asleep after a very short feed. Help from a breastfeeding specialist might identify poor positioning, latch, a tight frenulum (membrane under the tongue), high muscle tone, or find a combination of issues for adjustment. Once breastfeeding issues are addressed at six weeks, baby B gains more weight.

Growth faltering and supplements needed

baby-growth-chart-baby-C-web
Poor weight gain for four months (baby C)

Baby C’s weight had been faltering for four months. Although still bright and alert, baby C would be very small and health care workers would be concerned. Baby C might breastfeed constantly but without ‘driving’ his mother’s milk supply—which would be very low after four months of poor feeding. Donor milk or supplemental formula would be needed here to provide immediate calories while work began on building mother’s milk supply. A very underweight baby might initially bring back some of the top ups as his stomach would be used to small volumes. Within a day or so these babies often respond with a voracious appetite and might gain as much as 100g – 120g per day for the first few days, and continue with good catch-up gain—until baby reaches the weight they should have been.

Weight loss, hospital admission

baby-growth-chart-baby-D-web
Losing weight for three weeks (baby D)

Baby D continued to lose weight for nearly three weeks before being admitted to hospital for tests and supplemental feeds. In those first weeks, health care workers may have believed breastfeeding could pick up on its own. However, intervening with good breastfeeding management at the first sign of continued weight loss at three or four days of age could have avoided this high weight loss and potentially irreversible damage to this mother’s milk supply. There can be many reasons for low milk supply or seemingly no breast milk after delivery, while these are being addressed, a baby needs to be fed with donor milk or formula.

When to take action

Take action early

As soon as weight gain falters consistently, a health check from your baby’s doctor to rule out medical issues and a breastfeeding assessment from a specialist to get breastfeeding back on track, can prevent a cycle of further weight loss, sleepy baby, and low milk supply ending in formula supplements. There are lots of ways to increase a milk supply so that baby can gain 30-40g per day, but sometimes supplements will still be needed. If your health professional or breastfeeding helper doesn’t seem sure how to review breastfeeding, contact an IBCLC lactation consultant for a full assessment and see Baby Not Gaining Weight.

Don’t “wait and see”

Advice from health professionals, friends or family to wait and see what baby’s weight is like in a week/fortnight/month, under the assumption that it can take a while to get breastfeeding established, is time wasted when you could be identifying fixable reasons for low milk intake—and making sure your baby gets the calories he needs. Equally, advice to start topping your baby up with formula after each feed without looking at breastfeeding management, misses the opportunity to problem solve to get back to exclusive breastfeeding where possible.

baby being lowered onto weighing scales
Weigh your baby on a hard, level surface NOT a soft surface or bed

Breastfed baby gaining too much weight?

Babies above the 99.6th centile for height are almost always healthy 12. If a child’s weight is above 99.6th centile or if their weight and height centiles are very different, the advice from Department of Health (UK) is to calculate their body mass index (BMI). Over the age of two years, the BMI is the simplest way to measure whether a child is overweight or underweight. The Centers for Disease Control and Prevention (CDC) in the United States do not recommend BMI-for-age growth charts for children younger than two years of age 13. To plot weight against length for children under two years refer to the WHO Child Growth Standards for length/height.

Breastfeeding is thought protective against obesity in later life 14 15, however, certain health issues can be a cause of unusually high weight gain, so always stay in close contact with your health professional if you have any concerns about your baby’s weight.

Summary

Although breastfeeding is the normal and natural way to feed a baby, situations can arise where babies may not thrive. A growth curve that crosses two or more of the pre-drawn centiles on the WHO charts indicates growth faltering, but there’s no need to wait until this happens before taking action. Taking action as soon as there are growth concerns—by seeing your health professional and a breastfeeding specialist— can prevent compromising both your baby’s health and your milk supply later. The sooner a low milk supply is addressed the easier it is to fix it. If donor breast milk or formula supplements are needed, this doesn’t have to mean the end of breastfeeding—it is very important that your baby is getting the food they need. Contact your IBCLC lactation consultant for a tailor made care plan to get breastfeeding back on track and see Baby Not Gaining Weight for more information.

If you have any worries about your baby’s weight gain or growth contact your health care professional for help. This article is not intended to replace medical advice.

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