Each child has points plotted over time
When parents compare their child with a neighbour's child or a classmate, the question becomes ‘is he shorter? is he lighter?’. A growth chart is built to answer a different question: ‘how is this child doing against himself?’. Growth charts show the pattern of height and weight gain over time, and whether a child is growing proportionately [10]. The World Health Organization standards include charts for length or height, weight, weight-for-length, body mass index and head circumference, as well as growth-velocity standards [2].
One measurement shows where a child is today. Repeated points show whether the direction is expected or has changed in a way that needs understanding. KidsHealth gives an example: a child who grew along the same pattern until age 2 and then started growing much more slowly than other children, a change that might point to a health problem a doctor could see on the chart [10].
Growth-velocity standards mean a doctor does not have to wait until a child crosses a fixed threshold to notice undernutrition or overweight, because they help identify a child who is on the way to becoming under- or over-nourished [1].
Where do these standards come from?
The World Health Organization standards for children from birth to 5 years were built on a study in 6 countries from different regions of the world: Brazil, Ghana, India, Norway, Oman and the United States. It included 8,440 children raised in environments that minimised constraints to growth such as poor diets and infection [1]. The aim was to describe how children should grow when their needs are met, not simply to average the children who happen to exist [1]. The standards also establish the breastfed infant as the normative model for growth and development, so an infant's chart is read in light of feeding and health history [1].
WHO says these standards can be applied to all children everywhere, regardless of ethnicity, socioeconomic status or type of feeding [1]. For children and adolescents aged 5 to 19 there is a separate growth reference, built to join smoothly with the preschool standards at age 5 and to line up with the adult overweight and obesity cut-offs at 19 [3].
In the UK, for example, the UK-WHO charts describe optimal growth for healthy breastfed children, and the 2 to 18 year chart includes tools for puberty assessment, a BMI centile lookup and a comparison with parental height [5, 6].
A centile is not an exam grade
Centiles on the chart show where a child stands compared with children of the same age and sex. The higher the number, the bigger the child is than others for height or weight; the lower it is, the smaller [10]. It is a measure of position, not a verdict that a child is ‘good’ or ‘bad’.
MedlinePlus notes that some children are small for their age but still developing normally, and some are short or tall because their parents are [8]. That is why doctors read the chart alongside the child's overall well-being, environment and family background: are milestones being met? are there other signs of ill health? how tall and heavy are the parents and siblings? was the child born early? has puberty started? [10].
The reverse is also true: a high centile is no guarantee that all is well, because WHO counts childhood overweight as a form of malnutrition just as it counts undernutrition [11]. If height is your specific worry, read the article on short height and the growth curve.
When does a change on the chart need assessment?
The UK NICE guideline on faltering growth sets clear thresholds for clinicians. After the early days of life, concern starts if a child's weight falls across 1 or more centile spaces when birth weight was below the 9th centile, 2 or more spaces when it was between the 9th and 91st, or 3 or more spaces when it was above the 91st, or if current weight is below the 2nd centile for age [4].
In the first days after birth some weight loss is normal; it usually stops after about 3 or 4 days, and most babies are back to birth weight by 3 weeks. If a baby loses more than 10% of birth weight, or has not regained it by 3 weeks, the guideline calls for assessment and feeding support [4].
For height, when there is concern the mid-parental height is worked out. If the child's height centile is more than 2 centile spaces below what parental heights predict, this could suggest undernutrition or a primary growth disorder [4]. MedlinePlus explains that very slow or very fast growth can sometimes signal a gland problem or disease [8].
When weight falters: the wider picture
MedlinePlus uses the term ‘faltering weight’ in place of the older ‘failure to thrive’, and defines it as a child whose current weight or rate of weight gain is much lower than that of other children of similar age and sex [7]. Its criteria include a marked fall in weight or BMI from the child's previous track, or very slow weight gain in children under 2 [7].
Causes can be medical, such as genetic, hormonal or organ problems, or related to eating itself. Babies who gain weight poorly often lack interest in feeding, and constipation, excessive crying, sleepiness or irritability may appear [7]. A shortage of nutrients such as iron can affect appetite and energy, which is the subject of the article on iron deficiency in children.
Regular check-ups help detect faltering weight early, and normal growth can continue if the cause is found and treated in time [7]. Globally, WHO estimates that 149 million children under 5 were too short for their age in 2022, and 37 million were overweight or living with obesity [11].
Bring earlier measurements
Keep the vaccination card or any record showing weight, height and the date of measurement rather than relying on memory. A growth chart is built from every measurement since birth [7], and measuring itself needs age-appropriate equipment and technique, which is why WHO runs a full training course for health workers on measuring weight and length or height and interpreting the results [2].
It is normal for growth speed to change with age: between ages 1 and 2 a toddler gains only about 2.2 kg, with about the same gain each year from 2 to 5; growth is steady from 2 to 10, and a final growth spurt begins with puberty, somewhere between 9 and 15 [9]. A child who ‘eats less’ after the first year may therefore be normal as growth slows, and the article on children's appetite explains this in detail.
Do not wait for the next school measurement if the child loses weight, stops growing, becomes unusually tired, has persistent vomiting or diarrhoea, swallowing difficulty, marked thirst and urination, or loses a skill [7, 8]. Early assessment looks for the cause rather than pressuring the child to ‘finish the plate’.
Leave the visit with a clear picture
At a paediatric and nutrition visit, new measurements are plotted next to earlier ones, height is compared with parental height, and eating, activity, sleep and development are reviewed, so decisions rest on a trajectory rather than one number [4, 10]. If there is excess weight with other signs, insulin-resistance risk may be assessed, which is covered in the article on insulin resistance in children [3, 11].
If you are worried about your child's growth and want an individual assessment, you can book an appointment at the clinic and bring all earlier measurements. This is a practical next step, not a promised result, and the treating team will decide what suits your child after assessment [4].
