For every 1,000 babies born in the UK every year, one will have Down's syndrome.
Those babies grow up to be adults - many of whom attended mainstream schools and go on to find employment, form relationships and live independently.
But it hasn't always been that way.
- What is Down's syndrome?
Down’s syndrome is caused by the presence of an extra chromosome in a baby’s cells.
The condition affects people of all ages, races, religious and economic situations.
People born with the condition will have some form of a learning disability. It can affect a person’s ability to learn but it does not mean they cannot learn.
- How have perceptions of people with Down's syndrome changed over the years?
In the early part of the last century legislation was introduced which led to thousands with learning disabilities placed in institutions known as "long stay hospitals".
Following the introduction of the 1944 Education Act, children with Down’s syndrome were deemed “ineducable” and were denied an education.
Change began in the 1970s with the introduction of special educational schools.
And in the 1980s, legislation was introduced to ensure that people with learning disabilities had the right to receive services and support within their own communities. This included the right to attend mainstream schools.
Matthew Purnell is one of those people.
He attended a mainstream school in Cardiff and is now living independently with two jobs.
Matthew, Heidi and Rachel are all living with Down's syndrome. They told ITV News what some of their biggest achievements have been including finding relationships and employment.
Read more from our coverage of World Down Syndrome Day on the ITV News site:
The changing perceptions of people with Down's syndrome has been largely down to how the internet and social media has allowed families and people with Down's syndrome to connect with each other.
A video called '50 Mums, 50 Kids, 1 Extra Chromosome' was released by parents to mark World Down Syndrome Day last year.
It became one of the most popular not-for-profit videos, racking up around 145 million views and popularised the hashtag #wouldntchangeathing.
Due to its impact on changing perceptions of the condition, the people involved in that project decided to set up 'Wouldn't Change A Thing' as an organisation to continue their mission.
Watch the 2019 video below:
A project in Llanfyllin near Welshpool is helping people with Down's syndrome learn new skills by working in the community. For people like Rhian, it's helped her confidence and independence: