Down syndrome is a genetic condition where a person is born with an extra copy of chromosome 21. This means that they have a total of 47 chromosomes instead of 46. This can affect how their brain and body develop. People diagnosed with Down syndrome have happy and healthy lives with supportive care.
Down syndrome is a genetic condition where people are born with an extra chromosome. Most people have 23 pairs of chromosomes within each cell in their body, for a total of 46. A person diagnosed with Down syndrome has an extra copy of chromosome 21, which means their cells contain 47 total chromosomes instead of 46. This changes the way their brain and body develop.
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Down syndrome can affect anyone. It’s a genetic condition, and it doesn’t happen as a result of something that the parents did before or during pregnancy. The majority of Down syndrome cases happen randomly (sporadically). People don’t usually inherit Down syndrome in an autosomal dominant or recessive pattern during conception when the egg and sperm meet.
Research is ongoing to learn more about the risk factors of Down syndrome. Studies suggest that the risk of giving birth to a child with Down syndrome increases as the birthing parent ages. Women or people assigned female at birth (AFAB) who are 35 or older are more likely to have a child diagnosed with Down syndrome or another type of genetic condition. Since people AFAB younger than 35 have higher fertility rates, most babies with Down syndrome are born to people under 35.
Down syndrome is the most common chromosome-related condition in the United States. An estimated 6,000 babies are born with the condition in the U.S. every year, which equals about 1 in every 700 babies. There are about 200,000 people in the U.S. diagnosed with Down syndrome.
Down syndrome causes physical, cognitive and behavioral symptoms. Not all people with Down syndrome have all of these symptoms. Symptoms and their severity are different from person to person.
Physical signs of Down syndrome are usually present at birth and become more apparent as your baby grows. They can include:
As your child grows, additional symptoms can arise because of the way that their body developed in the uterus, including:
Your child’s healthcare provider will regularly check for these and other conditions that may cause additional symptoms throughout your child’s life.
Your child with Down syndrome may have cognitive development challenges as a result of their extra chromosome. This can cause intellectual or developmental disabilities. Your child’s ability to meet developmental milestones, or things that your child can do at a certain age, may differ from other children, including how they:
As a result, it may take your child longer to do the following things:
Your child diagnosed with Down syndrome may exhibit behavioral symptoms. This can be the result of your child not being able to communicate their needs to you or their caregivers effectively. Behavioral symptoms of Down syndrome could include:
An extra chromosome causes Down syndrome. Each human cell typically contains 23 pairs of chromosomes, which totals 46. Down syndrome occurs because of changes in the way cells in chromosome 21 divide. Every person with Down syndrome has an extra chromosome 21 in some or all of their cells.
There are three types of Down syndrome with different causes, including:
Trisomy 21 is the most common type of Down syndrome. The term “trisomy” means having an extra copy of a chromosome. Trisomy 21 occurs when a developing fetus has three copies of chromosome 21 in every cell instead of the typical two copies. This type makes up 95% of all cases of Down syndrome.
Translocation is a type of Down syndrome where there’s a partial or full amount of chromosome 21 attached to another chromosome. Unlike trisomy 21, translocation occurs when chromosome 21 isn’t separate, but it relocates to another numbered chromosome. This type of Down syndrome accounts for less than 4% of all cases.
Mosaic Down syndrome is the rarest type of Down syndrome and accounts for less than 1% of all cases. Mosaicism occurs when only some cells contain the usual 46 chromosomes and some cells contain 47. The extra chromosome in some cells is chromosome 21.
A healthcare provider can suspect Down syndrome during pregnancy with prenatal screening tests. They can also diagnose this condition during pregnancy with diagnostic tests.
These tests assess your risk of having a child with Down syndrome rather than giving you a confirmation of a diagnosis. Screening tests could be a blood test of the birthing parent’s blood to look for indicators of Down syndrome. Another screening test is an ultrasound. During this imaging test, your provider will look for signs of Down syndrome, like extra fluid behind your baby’s neck. It’s possible that a screening test could be normal and not show signs of Down syndrome when the condition is present.
Diagnostic tests during pregnancy can confirm a Down syndrome diagnosis. They usually take place after a positive screening test. Diagnostic testing offers more risk for the birthing parent and the developing fetus. Tests could include:
These tests can detect chromosomal changes that lead to a Down syndrome diagnosis.
After your baby is born, providers look for the physical signs of Down syndrome during a physical exam. To confirm the diagnosis, your baby’s provider may perform a blood test called a karyotype test. In this test, your baby’s provider will remove a small blood sample to study under a microscope. They’ll look for an extra 21st chromosome to diagnose the condition.
If you find out the fetus you’re carrying has Down syndrome, your providers will direct you to resources to help you after the birth of your baby. You may want to participate in counseling or join a support group. Counselors and support groups help you prepare for raising a child with Down syndrome.
In support groups, you can talk with other parents about their experiences raising a child with Down syndrome. It’s a great way to share practical advice on managing the condition, its frustrations and joys. These groups offer a sense of belonging and give you support, so you know you’re not alone.
There’s no cure for Down syndrome, but treatment is available to help your child reach their full potential. Treatment focuses on helping your child thrive physically and mentally. Treatment options could include:
If your child has Down syndrome, they’ll likely see a variety of specialists to make sure they’re healthy. Their care team may include:
People with Down syndrome may have other medical conditions that are either present at birth or develop over time. A healthcare provider can help you and your child manage these conditions. Common conditions of Down syndrome can include:
People with Down syndrome are at greater risk for developing Alzheimer’s disease. Alzheimer’s disease occurs in about 30% of people with Down syndrome in their 50s and about 50% of those in their 60s.
Studies show the extra full or partial chromosome contributes to this increased risk of Alzheimer’s. Genes on chromosome 21 produce amyloid precursor protein, which plays an important role in the brain changes seen in Alzheimer’s patients.
You can’t prevent Down syndrome since it’s a genetic condition. To learn more about your risk of having a child with a genetic condition, talk to your healthcare provider about genetic testing.
Children born with Down syndrome lead happy and healthy lives with supportive care. Treatment and therapies can help them reach developmental milestones, gain an education with their peers, build relationships and have successful careers.
Groups and resources are available for parents, family members and caregivers to help you best care for your child and support them.
No. Down syndrome is a lifelong condition, and there isn’t a cure. Symptoms of the condition are manageable, and treatment is available for any associated conditions that may arise.
The life expectancy for a person diagnosed with Down syndrome is 60 or older. They may need support and care throughout their entire life.
There are resources available to people with Down syndrome and their families. Many families join Down syndrome support groups to share their experiences and ways to help their children live a healthy, full life.
People with Down syndrome will likely need assistance throughout their lives. In addition to ongoing therapies, this could include help with education, employment and living independently. A variety of organizations offer resources to help educate and empower people living with Down syndrome and their families.
The National Down Syndrome Society and the National Association for Down Syndrome are two of the most common resources people use for more information and support.
People diagnosed with Down syndrome may have children of their own. An estimated 50% of women or people assigned female at birth (AFAB) can have children. It’s normal for men or people assigned male at birth (AMAB) to have a low fertility rate if they have Down syndrome. If a birthing parent has Down syndrome, the risk of passing the genetic condition onto their future children is 35% to 50%.
A note from Cleveland Clinic
It may feel overwhelming to learn that your child has Down syndrome. As you process the news, know that you’re not alone and that your child’s extra chromosome is part of what makes them unique. You can find support through your child’s medical care team or by joining groups for families and caregivers to learn more about the condition and how to help your child grow.
Last reviewed by a Cleveland Clinic medical professional on 01/31/2023.
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