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Down syndrome

Down syndrome

Published on 9 October 2025

Every year, around 750 babies in the UK are born with Down syndrome, a genetic condition which causes some level of learning disability.

The condition is caused by the presence of an extra copy of chromosome 21 in a baby's cells. It occurs by chance at conception and is irreversible. As yet, no one knows what causes the presence of the extra chromosome 21.

Estimates suggest around half to three quarters of children with Down syndrome suffer from a breathing disorder called obstructive sleep apnoea (OSA), which disturbs their sleep and can lead to problems with growth, learning and behaviour. Many also go on to have problems with their near vision, meaning they need glasses.