Down syndrome is not a disease, virus, or illness, either. It's a syndrome. You cannot pass it from one person to another. And you cannot do anything (right or wrong, during or before pregnancy) to make a person have Down syndrome.

So, we know what it's not ... then what is it?

A "syndrome" is made when a doctor (or other professional) puts together a bunch of characteristics that are found in a certain group of people. Those characteristics then become the symptoms or features of that syndrome. People with those features are then diagnosed with that syndrome.

The symptoms of Down syndrome are short stature, low set and small ears, small folds in the inside corner of the eye, small fingers and toes, and flattened facial features, among others. Those are symptoms that may give a hint to doctors that a newborn has Down syndrome. But, not everyone with Down syndrome may have those symptoms. And one person certainly cannot have all the symptoms of Down syndrome.

There are symptoms that make certain a person has Down syndrome, because everyone with Down syndrome has them. They are developmental delay and an extra chromosome 21.

So, that's what Down syndrome is!

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