How Much Do You Know About Down Syndrome? Here’s a Fact Sheet

by Irina Myriam . on 05/07/2025 6184

Down Syndrome is a genetic disorder seen in about 1 in 800 births.

Babies normally have 46 chromosomes, but people with Down Syndrome are born with an extra copy of chromosome 21.

Let’s learn more about the condition with some key facts.

1. Types of Down Syndrome

Trisomy 21

The most common type. It happens when there are 3 number 21 chromosomes in every cell of the body. About 95% of people diagnosed fall into this group.

Translocation

The second most common type, where a part of chromosome 21 breaks off and attaches to another chromosome. This happens in about 4% of cases.

Mosaic

The least common type, which occurs in about 1% of the population. Only some cells will have an extra copy of chromosome 21. People with this variant usually have fewer characteristics of Down syndrome.

2. Characteristic Physical Features
People with the condition typically have: Flattened face Eyes that slant upwards Small white spots on the iris Protruding tongue Small ears A palmar crease (a single line across the palm of the hand) Small hands and feet A short neck Poor muscle tone Short height relative to others

3. Risks Factors

The chance of a having a baby with Down syndrome increases if:

The mother is 35 years or older when pregnant
The parents have another child with Down syndrome
Mom or dad has the translocation chromosome (which can cause the translocation type of Down syndrome)

4. Developmental Delays

Every person with Down syndrome is different; each having their own abilities and talents.

Although children with the condition often meet age-related milestones, they may be slower at learning. They may also experience:

Delay in speech and language development
Cognitive impairment (ranging from mild to moderate)
Impulsive behaviour
Short attention spans

5. Health Complications

A lot of kids with Down syndrome don’t suffer from any major birth defects, but show the common facial features. Still, some might have medical complications. Here are some of the more common ones:

Gastrointestinal abnormalities
Heart defects
Spinal issues
Sleep apnea (interruption of breathing as one sleeps)
Hearing loss
Poor vision

6. Screening and Testing

It is possible to screen for Down syndrome during pregnancy. It usually involves a blood test from the mother and an ultrasound scan that creates a picture of the baby.

Testing is done after a positive screening test, to confirm a diagnosis for Down syndrome.

There are several tests that can be done, including amniocentesis (where a small amount of amniotic fluid is removed for testing) and chorionic villus sampling (involving a small sampling of cells from the placenta).

7. Treatments

There is no cure for Down syndrome. It is a lifelong condition.

However, there are many different treatments and therapy options that can highly benefit a child with Down syndrome—enabling a better chance at independence and the reaching of one’s potential. These include: