Down Syndrome

Medically Reviewed by Jabeen Begum, MD on February 23, 2024
13 min read

Down syndrome is a genetic condition that causes mild to significant physical and developmental problems.

People with Down syndrome (DS) are born with an extra chromosome. Chromosomes are bundles of genes, and your body relies on having just the right number of them. With Down syndrome, this extra chromosome leads to a range of issues that affect you both mentally and physically.

Down syndrome is named after John Langdon Down, an English doctor who was the first person to publish an accurate description of the condition in the 1860s.

Down syndrome is a lifelong condition. Although it can’t be cured, doctors know more about it now than ever. If your child has it, getting the right care early on can make a big difference in helping them live a full and meaningful life.

How many people have Down syndrome?

No one knows for sure. It could be as high as 6 million people worldwide, according to the Global Down Syndrome Foundation. The CDC estimated there were around 250,700 children, teens, and adults living with Down syndrome in the U.S. in 2008. It also said 1 in every 700 babies in the U.S. are born with Down syndrome. This makes it the most common chromosomal condition in America.

Down syndrome vs. autism

There are some similarities and differences between the two conditions. First, we'll look at the differences.

Down syndrome: Genetic disorder, usually with physical traits. People with this condition are often social and friendly. Their language development is similar to that of more typical children.

Autism: Neurological disorder (dysfunction in the brain and nervous system) with no physical characteristics. People with this condition often prefer to be alone and not socialize. Their language skills might be delayed or not develop.

Similarities: Both groups may:

  • Prefer routine
  • Have developmental delays
  • Avoid eye contact
  • Enjoy repetitive play 
  • Show challenging behaviors (trouble managing feelings when frustrated, lack of impulse control, etc.)

About 18% of children with Down syndrome also have autism, but sometimes children with DS might show these behaviors without having autism.

There are three types of Down syndrome: trisomy 21, translocation Down syndrome, and mosaic Down syndrome.

Trisomy 21

This is the most common type of Down syndrome, with 95% of people with DS having trisomy 21. Here, all your body's cells have three copies of chromosome 21 instead of two.

Translocation Down syndrome

About 3% of people with Down syndrome have this type, where there's an extra part or whole chromosome 21, but it's attached to another chromosome instead of being a separate chromosome 21.

Mosaic Down syndrome

This type of Down syndrome, which affects about 2% of people with the condition, happens when only some cells in your body have an extra chromosome 21. 

You can’t tell what type of Down syndrome someone has by how they look. The effects of all three types are very similar, but someone with mosaic Down syndrome may not have as many symptoms because fewer cells have the extra chromosome. So it's possible to have undiagnosed mosaic Down syndrome.

Down syndrome can have many effects, and it’s different for each person. Some will grow up to live almost entirely on their own, while others will need more help taking care of themselves.

Mental abilities vary, but most people with Down syndrome have mild to moderate issues with thinking, reasoning, and understanding. They’ll learn and pick up new skills their whole lives, but they may take longer to reach important goals like walking, talking, and developing social skills.

People with Down syndrome may also have trouble with behavior – they may not pay attention well, or can be obsessive about some things. That’s because it’s harder for them to control their impulses, relate to others, and manage their feelings when they get frustrated.

As adults, people with Down syndrome may learn to decide many things on their own but will likely need help with more complex issues, like birth control or managing money. Some may go to a college that can provide accommodations and modifications tailored to developmental and intellectual delays and may go on to live independently, while others will need more day-to-day care.

Down syndrome features

People with Down syndrome tend to have certain physical features in common. These may include:

  • Eyes that slant up at the outer corner
  • Small ears
  • A flat nose
  • Tongue that sticks out
  • Tiny white spots in the colored part of the eyes
  • Short neck and overall height
  • Small hands and feet
  • Short stature
  • Loose joints
  • Weak muscle tone and joints
  • Small pinky fingers that curve in
  • One crease across the palm of the hand

Many people with Down syndrome don’t have any other health issues, but others do. They may have eye diseases, vision problems, hearing loss and ear infections, sleep apnea, and heart problems.


For most people, each cell in the body has 23 pairs of chromosomes. One chromosome in each pair comes from your mother and the other comes from your father.

But with Down syndrome, you get an extra copy of chromosome 21. That means you have three copies instead of two, which leads to the symptoms of Down syndrome. Doctors aren’t sure why this happens. There’s no link to anything in the environment or anything the parents did or didn’t do.

Is Down syndrome genetic?

It’s not common, but it's possible to pass Down syndrome from parent to child. Sometimes, a parent has what experts call “translocated” genes. That means some of their genes aren’t in their normal place, perhaps on a different chromosome from where they’d usually be found.

The parent doesn’t have Down syndrome because they have the right number of genes, but their child may have translocation Down syndrome, where they have an extra chromosome 21. Not everyone with translocation Down syndrome gets it from their parents – it may also happen by chance.

While doctors don’t know what causes it, they do know that women (or people with female anatomy) ages 35 and older have a higher chance of having a baby with Down syndrome. If you’ve already had a child with Down syndrome, you’re more likely to have another one who also has it. But most babies who have Down syndrome are born to mothers under 35 because most children are born to younger women.

Men (or people with male anatomy) over 40 at the time of conception also have an increased risk of having a child with Down, particularly if the mother is also over 35. 

Routine tests done during pregnancy can check to see if it’s likely your baby has Down syndrome. If those results are positive, or if you’re at high risk, you may choose to have some more invasive tests to be sure.

Prenatal genetic testing

Screening tests are usually done first and are considered to pose no risk to you and your growing baby. These normally include a combination of blood tests and ultrasounds, which show images of your baby.

In the first trimester, you may have:

  • Blood tests. Your doctor measures the levels of a protein called PAPP-A and a hormone called hCG in your blood. Anything out of the normal range could mean a problem with the baby. 
  • Cell-free DNA test. This blood test checks the baby's DNA circulating in your blood via the placenta. It can tell if your unborn baby is at a higher risk of a chromosomal abnormality like Down syndrome or another condition. 
  • Ultrasound (nuchal translucency test). Your doctor looks at a picture of your baby and measures the folds of tissue at the back of their neck. The extra tissue is called the nuchal fold. Babies with Down syndrome tend to have extra fluid there. Since this fluid buildup can be due to a number of genetic conditions, this test is usually combined with a blood test.

In the second trimester, you may have:

  • Blood tests. Either a triple or quad-screen test measures other substances in your blood, including the protein AFP and the hormone estriol. Those levels, combined with the results from the first-trimester tests, give your doctor a good estimate of the chances your baby has Down syndrome.
  • Ultrasound. When your baby is more developed, an ultrasound can show some of the physical features of Down syndrome.

Screening tests don't tell you for certain that your baby has Down syndrome. They only tell you if your baby is at high or low risk for DS. For confirmation, you have to do a diagnostic test. These diagnostic tests usually happen after screening test results are positive, as they carry a small risk that you could miscarry after having them. They include:

  • Chorionic villus sampling (CVS). This can be done during the first trimester, using cells taken from the placenta.
  • Amniocentesis. Fluid is taken from the amniotic sac surrounding the baby, usually during the second trimester.
  • Percutaneous umbilical blood sampling (PUBS). This is also done in the second trimester using blood removed from the umbilical cord.

After a baby is born, a doctor may suspect Down syndrome in a newborn based on the baby’s appearance. But some babies without DS may have similar physical features to a baby with Down syndrome.

A diagnosis can be confirmed by a blood test called a karyotype test that lines up the chromosomes and will show if there’s an extra chromosome 21.

Babies with Down syndrome may be born with other physical problems, and they’re at a higher risk of certain health issues later in life.

Possible complications of Down syndrome include:

  • Heart problems. About half of babies with Down syndrome are born with a heart defect that may need surgery.
  • Hearing and vision problems, including crossed eyes and cataracts
  • Gastrointestinal disorders like blockages, reflux, and celiac disease
  • Weight issues
  • Breathing issues, including sleep apnea, asthma, and pulmonary hypertension
  • Underactive thyroid
  • Seizures
  • Childhood leukemia
  • Early-onset dementia

They’re also more likely to have:

  • Blood conditions like anemia, where you have low iron. It’s not as common, but they also have a higher chance of getting leukemia, a type of blood cancer.
  • Infections. People with Down syndrome may get sick more often because they tend to have weaker immune systems.

As they age, adults with Down syndrome are at a higher risk of depression and Alzheimer's dementia, which are conditions that will also affect their behavior.



There’s no specific treatment for Down syndrome. But there is a wide range of physical and developmental therapies designed to help people with Down syndrome reach their full potential. 

The earlier you start treatment, the better. Children with Down syndrome can usually hit the same milestones as other children but at later stages. So, therapy is key to help children with the disorder meet those milestones.

Each child will have different needs. Yours may benefit from:

  • Physical, occupational, and speech therapy.  Physical and speech therapists can help your child with sitting and walking properly, developing speech, and learning to communicate. Occupational therapists teach everyday skills like how to get dressed, eat, or use a computer.
  • Behavioral counseling. Children with Down syndrome may also have conditions like ADHD, autism, or compulsive behaviors that need to be addressed.
  • Specialized education services. By law in the U.S., children with Down syndrome can get free educational services and devices to help with learning. This assistance lasts until age 21 or when they finish high school, whichever comes first. 
  • Social and recreation activities
  • Programs that offer job training and teach self-care skills

You’ll also work closely with your child’s doctor to watch for and manage any health problems that come with the condition.

Individualized education program (IEP)

This is a legal written document required for each child who needs special educational services in the U.S. The IEP is written by school personnel (teachers, school psychologist, etc.) after meeting with you and setting developmental goals for your child for the year. This also helps you decide whether to place your child in a school for kids with special needs or in one where most of the kids don't have special needs. A new IEP is written each year. 

When your child has Down syndrome, one of the most useful things you can do is learn as much about it as you can. You might search online for programs and resources to help your child.

Along the way, talk with other parents whose children have Down syndrome so you can learn tips and find out what to expect. And as your child grows, you can work with doctors, therapists, teachers, and other specialists.

Beyond these big-picture tasks, it can help to know what you can do day to day, not only to support your child, but also to take care of yourself.

Down syndrome support

Every family has their joys, stresses, and challenges, but when you have a child with Down syndrome, things look a little different. Besides juggling school, music lessons, sports, and jobs, you typically have a lot of extra visits with doctors and therapists.

Your needs and the needs of your child make it even more important to accept help when it’s offered. Here are a few ideas:

  • Build a support system. Invite your friends and family to take part in caregiving. They can let you have a little time to yourself to walk, read a book, or just zone out for a while. A break, even a small one, can help you be a better parent and partner.
  • Talk about your challenges. People want to help but don’t always know how. A simple, “It’s hard to get a healthy dinner on the table with all these appointments” opens a door and gives them ideas of what they can do.
  • Keep a list of things you need. And don’t be afraid to use it. Next time someone says, “Just let me know how I can help,” you’ll be ready.
  • Find time for friends. Even if it’s just a small moment after the kids go to bed, friends can help you laugh and recharge.
  • Consider therapy. You might think about seeing a therapist. They can help you work through your feelings and give you tools to handle everyday stresses.
  • Take care of your health. Exercise and eat well, even when you feel burned out. Try to make a plan and stick to it as best you can.

Everyday tips

Like most children, kids with Down syndrome tend to do well with routine. They also respond better to positive support than discipline. Keep both of those things in mind as you try the following daily tips:

  • Give your child chores around the house, but break them up into small steps and be patient.
  • Have your child play with other kids who do and don’t have Down syndrome.
  • Keep your expectations high as your child tries and learns new things.
  • Make time to play, read, have fun, and go out together.
  • Support your child in doing day-to-day tasks on their own.

For everyday tasks, you can try to:

  • Create a daily schedule and stick to it as best you can. For example, the morning might be getting up, eating breakfast, brushing teeth, and getting dressed.
  • Help your child change from one activity to the next with very clear signals. For younger kids, seeing a picture or singing a song can help.
  • Use pictures to make a daily plan your child can see.
  • Use simple terms when talking to your child, with fewer steps.
  • Encourage your child to repeat directions back to you. This helps to make sure they understand.
  • Name and talk about things your child seems excited about.

To help your child with school, you might:

  • Avoid saying “That’s wrong” to correct mistakes. Instead, say, “Try it again.” Offer help if it’s needed.
  • As you work with doctors, therapists, and teachers, focus on your child’s needs rather than on the condition.
  • Look at what your child is learning at school and see if you can work those lessons into your home life.

It's also important for all kids to feel like they have some control over their lives. It’s even more important for kids with Down syndrome, and it’s one way to help them live a fulfilling life. To do this, you can:

  • Let your child make choices when it makes sense to. This can be as simple as letting them choose what clothes to wear.
  • Allow them to take reasonable risks. This is a challenge every parent faces. You need to protect your children, but you should also let them see what they can handle.
  • Support them in solving problems, like how to deal with an issue with friends or approach a problem at school. You don’t have to fix it for them, but you can help them do it themselves.

People with Down syndrome are born with an extra chromosome. This can lead to a range of issues that affect them mentally and physically. Nowadays, there are a lot of interventions to help people with DS lead fulfilling and productive lives.

What is the life expectancy of someone with Down syndrome?

The lifespan for people with Down syndrome has increased over the years. In the 1980s, the lifespan was about 25 years. Now, it's around 60 years.

Can Down syndrome be diagnosed later in life?

Yes. Most people with DS are either diagnosed before birth through genetic testing or at birth based on physical appearance. But people with the rare mosaic Down syndrome may grow to adulthood without being aware they have it. This is probably because they may not have the typical physical features of someone with Down syndrome. Only some of their body cells have three copies of chromosome 21, while with the more common trisomy 21, every cell has three copies of chromosome 21.

Can people with Down syndrome have children?

About half the women with Down syndrome are fertile, but most of the men with this condition are infertile. The few children born to men who had DS didn't inherit the condition. But for women with DS, about a third gave birth to children who also had it.