What causes Down syndrome?

Down syndrome is caused by the presence of an extra copy of chromosome 21. Normally, a person has 46 chromosomes (23 pairs), but individuals with Down syndrome have 47.

This extra genetic material changes the way the body and brain develop, leading to the physical and intellectual traits of the condition. There are three main types: Trisomy 21 (the most common), Mosaic Down syndrome, and Translocation Down syndrome.

It’s important to note that nothing a parent does before or during pregnancy causes Down syndrome—it happens naturally as part of cell division.

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