Author: Dr Daniel CHIU
Director, Hong Kong Paediatrics Foundation
Daniel is 3 years old. He is healthy and happy. He has recently joined an international kindergarten. His mother is very worried as she finds out that he is the shortest in the class. His mother wants to know what to do.
Short stature commonly causes great emotional tolls for parents. People usually label a child as short when his height is significantly lower than the mean for children of that gender, age and race (>= 2 standard deviations or below 3rd percentile on a growth chart). Short stature may be a variant of normal growth and only less than 20% might indicate an underlying disease. Parents show know these basic facts about growth:
- Size of a baby at birth is determined more by maternal nutrition and pregnancy factors than by genetic makeup.
- Genetic potential affecting height shows up after two years old. Correlation between length at 2 years and adult height is 0.80
- Most children are born with a length around 50 cm (46-53 cm)
- Normally, children grow fast in the first year of life (from 50cm to 75 cm). Slower but still fast growth is observed in the second year (from 75cm to 85 cm). Growth rate gets steady thereafter (around 5-9 cm/year when age 2-6 years, and 4-6 cm/year after 6 years old till puberty).
- For comparison, it is best to measure the child’s height at specific time of the day and at intervals (say, every 2 months for the first year, every 3 months for the second year and every 6 months thereafter.)
- Many children who are short for their age are normal and might reach normal height as adults. Short children with normal height velocity usually do not have medical illness. They are short because of genetic / familial factors or constitutional delay in growth.
- Less that 20% of short children are due to medical causes. These include chronic illness affecting the heart, lungs, intestines, or kidneys. Hormonal or metabolic factors, chronic steroid or drugs used in treating ADHD, bone diseases, gene defects, chronic malnutrition and chronic stress might also lead to short stature.
- Most importantly, parents should take an overview of the child’s health and development, and how they have progressed over time, and not just focus on height and weight.
A growth chart uses percentile lines to display the growth trajectory for a child of a certain age, gender, and race. Each line indicates a certain percentage of the population who would be at that particular height at a particular age. Children often do not follow these lines exactly, but their growth over time is roughly parallel to these lines. A child who has a height plotted below the third percentile line is considered to have short stature and warrants medical attention.
Regular measurements of a child’s height, weight and head size and plotting them on a growth chart are essential to see if your child is growing as expected. It is a common mistake to view growth chart as grades in school. If a boy’s height is plotted on the 25th percentile line, for example, this indicates that approximately 25 out of 100 boys of his age is shorter than him. However, it does not mean he is more unhealthy than the child at the 90th. Parents should not endeavour to push up the percentiles by giving excessive nutrition to the children. This can do more harm than good. What we care about most is the trend at which a child grows physically, not the number. What we must watch out for is an abnormal trend, such as the line is crossing percentiles on the grid.
Growth (height) velocities
Height velocity is one of most sensitive indicators of illness. From 2-4 years, velocity is 5.5 cm/ year and from age 4-6 years, velocity is less than 5 cm/year. From 6 years to puberty, an increase of 4 cm per year is expected. During puberty, peak height velocity is 6 to 12 cm/year in males and 5 to 10 cm/year in females. A reduction in velocity (less than 25% for age) is a strong indication for intervention.
Prediction of adult height
Adult height is determined by a combination of genetic potential, illness and environment factors. No method accurately predicts adult height, but an estimate of a child’s genetic height potential can be obtained by calculation of the mid-parental height. Below is a simple equation
- For girls in cm, (Sum of parents’ height) /2 – 6.5
- For boys in cm, (Sum of parents’ height) /2 + 6.5
This is just a very rough estimate of the average height of how tall a child will be when fully grown. A margin of error of about 8.5 cm up (97%) or down (3%) is expected.
Actions to be taken when your child is suspected to be short
When your child is short (<3%), do not just sit and hope your child will catch up later. Delayed appropriate treatment might lead to irreparable outcomes.
Following the follow steps is advised:
- Measure your child’s height properly and serially
- Choose the right growth chart (appropriate age, gender and race) and plot your child’s height.
- Calculate the growth velocity and plot on growth velocity chart
- Measure height of both parents and predict child’s adult height
- Collect information as shown in Box A
- Check whether your child has features shown in Box B
- Consult your doctor if:
- Your child’s height is below 3% at growth chart
- Growth velocity is less than 25th percentile for age
- Height-for-age curve has deviated away across 2 percentile curves (eg from above 25th percentile to below 10%)
- Child’s projected height is more than 8.5 cm below mid-parental height.
- Is not only short but also grossly thin
- Your child has medical problems or abnormal features (Box B)
- No sign of puberty by 12 years old for girls and 14 years old for boys.
A. Basic Essential Data
- Pregnancy history
- Birth history
- Growth data (height, weight and head circumference) at birth and progress
- Developmental history
- Feeding and dietary history
- Medical illness and medication
- Parental height, growth pattern and puberty onset
B. Abnormal Features
- Wasting or obesity
- Abnormal facial, neck and chest features
- Abnormal limbs
- Delayed development