What is Down’s syndrome?

Down’s syndrome is a genetic condition caused by an extra chromosome. Typically, babies are born with each cell containing 23 pairs of chromosomes, or 46 chromosomes in total. 

In babies with Down’s syndrome, chromosome 21 doesn’t separate properly and instead splits into three, rather than two. This extra chromosome is responsible for the cognitive and physical features of Down’s syndrome.

It is important to note that Down’s syndrome is not a disease or an illness, but a condition or syndrome, and many people with Down’s syndrome go onto have jobs and live independently, living happy and fulfilled lives.

Why is it called Down's syndrome?

Down’s syndrome is named after the English doctor, John Langdon Down, who was the first to categorise the common features of people with the condition. However, it was actually Dr. Jerome Lejeune who discovered the syndrome as a genetic condition, whereby a person has three copies of chromosome 21 instead of two.

What causes Down’s syndrome?

In all cases of reproduction, both parents pass their genes onto their children, which are carried in chromosomes. Half of the chromosomes are from their mother, and half are from their father. In spite of this, most cases of Down's syndrome are not inherited, but occur by chance at the time of conception. 

Scientists do not know what causes the presence of an extra chromosome 21 and there is no way of predicting whether a person is more or less likely to make an egg or sperm with an extra chromosome.

Interestingly, there is a known link with advanced maternal age and Down’s syndrome, although the reasons for this are unknown. However, most babies with Down’s Syndrome are born to women under the age of 35, as younger women have higher fertility rates.

What is clear is that nothing done before, during or after pregnancy can cause Down’s syndrome, it happens by chance. It occurs in all races, ethnicities, social classes and countries throughout the world.

Is Down’s syndrome a learning disability?

Down’s syndrome is not a learning disability in itself, but often causes some form of learning (or intellectual) disability. In fact, it is the most common genetic cause of learning disability, affecting approximately 1 in every 1,000 children globally.

A person with Down’s syndrome will typically have some degree of learning disability, but the level of ability will be different for each individual. Usually, Down’s syndrome will result in mild to moderate intellectual impairment and a lowered IQ. However, thinking and learning problems are rarely severe and many individuals with Down’s syndrome go onto pursue higher education.

A child with Down’s syndrome might take longer than other children their age to reach certain milestones and to develop certain skills. This is because children with Down’s syndrome often have delays in speech and motor skills, which means they may need ongoing support for different aspects of their life when they become an adult.

Are there different types of Down’s syndrome?

There are three different types of Down’s syndrome. Trisomy 21 is the most common form, affecting 95% of those with Down’s syndrome. With this particular form, every cell in the body has three copies of chromosome 21 instead of two.

Another form of Down’s syndrome is called translocation Down’s syndrome. In this type, each cell has part of an extra chromosome 21, or an entirely extra one. But it’s attached to another chromosome instead of being on its own.

Mosaic Down's syndrome is the rarest type, where only some cells have an extra chromosome 21. Someone with this type of Down’s syndrome may not have as many characteristics as those who have translocation or Trisomy 21, because fewer cells have the extra chromosome.

How is Down’s syndrome diagnosed?

Down’s syndrome can be confirmed by a blood test called a karyotype test, that lines up the chromosomes and will show if there’s an extra chromosome 21.

How common is Down’s syndrome?

  • For every 1,000 babies born, one will have Down’s syndrome.
  • About 750 babies with Down’s syndrome are born in the UK each year.
  • Down’s syndrome affects people of all ages, races, religious and economic situations.
  • There are approximately 40,000 people with Down’s syndrome living in the UK.

What are the characteristics of Down’s syndrome?

People with Down's syndrome will often share similar physical features. They tend to have a small nose with a flat nasal bridge, a small mouth, eyes that slant upwards, a short neck, and restricted growth. People with Down's syndrome will also tend to have movement and speech delay due to anatomical and physiological differences, such as low muscle tone.

People with Down's syndrome also have an increased risk of a number of different health problems, including heart and gastrointestinal problems. However, today the average life expectancy for a person with Down’s syndrome is 60 years old, with some living into their seventies.

What language should we use when talking about Down’s syndrome?

The language we use when discussing Down’s syndrome is extremely important and helps frame perceptions. The campaign Language Creates Reality explores the issue in depth and provides readers with appropriate words and phrases to use when discussing Down’s syndrome.

For example, instead of saying “a Down's syndrome baby”, we should say “a baby with Down’s syndrome”. In this way, we are reminded that a disability does not define an individual. Person-centred language conveys respect and emphasises that people with disabilities are first and foremost, people.

Similarly, the word “typical” is preferred over “normal”, as saying a child without a syndrome is normal can cause offense.

The campaign also draws on how language is used in a medical setting, for instance, when parents are told their child is likely to have Down’s syndrome. “There is a high chance your baby has Down's syndrome” is a much more neutral way of saying “there is a high risk”. Language used early on can have a powerful emotional impact on parents.

Similarly, we shouldn’t say “suffers from Down’s syndrome” but “has Down syndrome”, as it is a syndrome, not an illness or an injury. By using non-judgmental, accurate and balanced language we can break down stigmas and misconceptions that surround Down’s syndrome.

Support group resources

  • For support, information or advice on any question or concern you have related to Down’s syndrome, the Down's Syndrome Association have specialist advisers you can talk to. 
  • The Down's Syndrome Association also have easy read documents, information on benefits and financial help, adult support and social care, and many other helpful resources
  • For information on support groups in the UK, please visit The Down Syndrome Development Trust's website.

Down’s syndrome in the news

To keep up to date on Down's syndrome in the news, please visit: 

Where to go for more information

There are various organisations which offer further information about Down's syndrome for individuals with the syndrome and their families, including: Down’s Syndrome Association, Down Syndrome Development Trust, National Down Syndrome Society.