Answering Common Questions About Down Syndrome

Down syndrome is the most common chromosomal genetic condition in humans. Around 5,700 babies are born with Down syndrome in the United States every year, that’s about 1 in every 640 babies.  To help more people understand Down syndrome, we’re sharing some of the most common questions about it.  

What is Down Syndrome? 

Down syndrome is a chromosomal condition. It occurs when a person is born with an extra copy of chromosome 21. This extra chromosome can affect a person's physical and mental development. It can also put a child at risk for other health conditions.  

Typically, humans have 46 chromosomes per cell. When a child is conceived, they receive 23 sets of chromosomes per parent, giving them 46 chromosomes per cell. However, when a person has Down syndrome, they usually have 47 chromosomes per cell. 

What Causes Down Syndrome? 

There is no specific cause of Down syndrome; the condition is caused by an error in cell division at the time of conception. 

According to the National Institutes of Health, this error occurs randomly. There are three types of Down syndrome. Only one type can be passed genetically, and it makes up only 4% of total Down syndrome cases. 

What Are the Different Types of Down Syndrome? 

There are three types of Down syndrome. Each type of Down syndrome is caused by a different chromosomal change. The three types are: 

Trisomy 21: Nearly 95% of all Down syndrome cases are Trisomy 21. This condition occurs when a fetus has three copies of chromosome 21 instead of the usual two. This chromosome error happens when a sperm or egg does not separate correctly during conception, causing the extra chromosome to be replicated in every cell of the body.   

Translocation: This type of Down syndrome happens when an extra copy of chromosome 21 breaks off but attaches itself to another chromosome. Like Trisomy 21, a fetus will have three copies of chromosome 21, but in this case, the extra chromosome stays attached to a different chromosome instead of being copied in all other cells of the body. Translocation is the only type of Down syndrome that can be passed genetically, and it makes up about 4% of total Down syndrome cases. 

Mosaicism: Mosaicism Down syndrome is when some cells have 46 chromosomes and others have 47. To determine if a child has mosaicism Down syndrome, a doctor will perform a blood test to analyze the number of chromosomes per cell. Individuals with this type of Down syndrome may have fewer characteristics associated with the condition. Mosaicism Down syndrome accounts for 1% of all cases. 

What are the Common Physical Traits of Down Syndrome? 

There are some physical traits that are common among people with Down syndrome. Typically, these physical conditions are present at birth but can manifest as a baby starts to grow. Some of the most common physical traits of Down syndrome are: 

• Weaker than usual muscle tone, usually seen at birth 
• A single crease in the palm of their hand, often called a palmar crease 
• Smaller than average ears, hands, and feet 
• Almond-shaped eyes that can point upwards with a fold over the eyelid 
• Shorter than average neck with excess skin 
• Specific facial features that can include a flattened nose 

Babies born with Down syndrome may not reach growth milestones as quickly as their peers. As they grow and receive care, children with Down syndrome can and will reach their milestones; it just may take a little longer.   

What are Health Conditions Related to Down Syndrome? 

Children born with Down syndrome have an increased risk of developing various health problems. Parents can check with their doctors during wellness exams and routine visits to screen for any related conditions.  

Some of the most common health conditions related to Down syndrome are: 

• Heart defects, which are commonly discovered at birth 
• Ear infections and sometimes hearing loss 
• Obstructive sleep apnea  
• Thyroid issues, routine tests are recommended 
• Vision problems, 60% to 80% of individuals with Down syndrome have some sort of vision complications 
• Gastrointestinal abnormalities 

Some of the health conditions listed above can be detected at birth, but others require regular doctor visits and testing. 

Are There Treatments for Down Syndrome? 

There are no individual or specific treatments for Down syndrome. However, there are multiple programs that help enhance the quality of life for people with Down syndrome.  

As a child grows, they often receive treatment from a team of support professionals. That team can include social workers, physical therapists, speech therapists, occupational therapists, special-education teachers, and their own physician. 

Can Early Intervention Help with Down Syndrome? 

The best way to set up a child with Down syndrome for success is with early intervention. For all children, the first year of their life is critical for future development. In most cases, Down syndrome is diagnosed at birth and starting therapy as soon as possible can help a child live a long and happy life.  

Early intervention starts at birth and can go on until the age of three. Babies are started with three critical therapies: occupational, speech, and physical. The goal is to help babies and children reach their milestones and accelerate their development.  

Through the Individuals with Disabilities Education Act, the U.S. Department of Education children with disabilities can receive benefits and education that aid in early intervention. 

If you would like to learn more about Down syndrome, we recommend checking out the National Down Syndrome Society, the Global Down Syndrome Foundation, and the National Institute of Health.