Down Syndrome

What Is Down Syndrome?


  1. Down syndrome is the most common genetic disorder in America.
  2. People with Down syndrome have mild to moderate disabilities.
  3. There are many supportive programs for people with Down syndrome and their families, helping people with Down syndrome to live healthy and fulfilling lives.

Down syndrome (sometimes called Down’s syndrome) is a condition in which a child is born with an extra copy of their 21st chromosome (hence its other name, Trisomy 21). This causes physical and mental developmental delays and disabilities.

Many of the disabilities are lifelong and they can also shorten life expectancy. However, people with Down syndrome can live healthy and fulfilling lives. Recent medical advances as well as cultural and institutional support for people with Down syndrome and their families provide many opportunities to help overcome challenges.

What Causes Down Syndrome?

According to the National Down Syndrome Society (NDSS), about 1 in 700 babies in the United States is born with Down syndrome. It’s the most common genetic disorder in the United States.

A quick explanation of basic genetics can help you understand how it happens. In all cases of reproduction, both parents pass their genes on to their children. These genes are carried in chromosomes. When the baby’s cells develop, each cell is supposed to receive 23 pairs of chromosomes (46 chromosomes total). Half of the chromosomes are from the mother and half are from the father.

In children with Down syndrome, one of the chromosomes doesn’t separate properly. The baby ends up with three copies, or an extra partial copy, of chromosome 21, instead of two. This extra chromosome causes problems as the brain and physical features develop.

Types of Down Syndrome

There are three types of Down syndrome:

Trisomy 21

Trisomy 21 means there is an extra copy of chromosome 21 in every cell. This is the most common form of Down syndrome.


Mosaicism occurs when a child is born with an extra chromosome in some but not all of their cells. People with mosaic Down syndrome tend to have fewer symptoms than those with trisomy 21.


In this type of Down syndrome, children have only an extra part of chromosome 21. There are 46 total chromosomes. However, one of them has an extra piece of chromosome 21 attached.

Will My Child Be at Risk for Down Syndrome?

Certain parents have a greater risk of giving birth to a child with Down syndrome. Mothers age 35 and older are more likely to have a baby with Down syndrome than younger mothers. The risk increases the older the mother is. Research shows that paternal age also has an effect — one 2003 study found that fathers over 40 had twice the risk of having a child with Down syndrome.

Other parents who are at greater risk of having a child with Down syndrome include:

  • people with a family history of Down syndrome
  • people who carry the genetic translocation

It’s important to remember that no one of these factors mean that you will definitely have a baby with Down syndrome, but statistically and over a large population, they can put you at higher risk.

What Are the Symptoms of Down Syndrome?

Though the likelihood of carrying a baby with Down syndrome can be estimated by screening during pregnancy, you won’t experience any symptoms of carrying a Down syndrome child.

At birth, babies with Down syndrome usually have certain characteristic signs, including:

  • flat facial features
  • small head and ears
  • short neck
  • bulging tongue
  • eyes that slant upward
  • oddly shaped ears
  • poor muscle tone

An infant with Down syndrome can be born at normal size but will develop more slowly than a child without the condition.

People with Down syndrome usually have some degree of mental disability, but it’s often mild to moderate. Mental and social development delays may mean that the child could have:

  • impulsive behavior
  • poor judgment
  • short attention span
  • slow learning capabilities

Medical complications often accompany Down syndrome. These may include:

  • congenital heart defects
  • hearing loss
  • poor vision
  • cataracts (clouded eyes)
  • hip problems, such as dislocations
  • leukemia
  • chronic constipation
  • sleep apnea (interrupted breathing during sleep)
  • dementia (thought and memory problems)
  • hypothyroidism (low thyroid function)
  • obesity
  • late tooth growth, causing problems with chewing
  • Alzheimer’s, in later life

People with Down syndrome are also more prone to infection. They may struggle with respiratory infections, urinary tract infections, and skin infections.

Screening for Down Syndrome During Pregnancy

Screening for Down syndrome is offered as a routine part of prenatal care in the United States. If you are a woman over 35, your baby’s father is over 40, or there’s a family history of Down syndrome, you may want to get an evaluation.

First Trimester

An ultrasound evaluation and blood tests can look for Down syndrome in your fetus. These tests have a higher false-positive rate than tests done at later pregnancy stages. If results aren’t normal, your doctor may follow up with an amniocentesis after your 15th week of pregnancy.

Second Trimester

An ultrasound and quadruple marker screen (QMS) test can help identify Down syndrome and other defects in the brain and spinal cord. This test is done between 15 and 20 weeks.

If any of these tests aren’t normal, you will be considered at high risk for birth defects.

Additional Prenatal Tests

Your doctor may order additional tests to detect Down syndrome in your baby:

  • Amniocentesis: Your doctor takes a sample of amniotic fluid to examine the number of chromosomes the baby has. The test is usually done after 15 weeks.
  • Chorionic villus sampling (CVS): Your doctor will take cells from your placenta to analyze fetal chromosomes. This test is done during the ninth and 14th week of pregnancy. It can increase your risk of a miscarriage, but only by less than 1 percent.
  • Percutaneous umbilical blood sampling (PUBS, or cordocentesis): Your doctor will take blood from the umbilical cord and examine it for chromosomal defects. It’s done after the 18th week of pregnancy. It has a higher risk of miscarriage, so it’s performed only if all other tests are uncertain.

Some women choose not to undergo these tests because of the risk of miscarriage. They would rather risk having a child with Down syndrome than losing the pregnancy.

Tests at Birth

At birth, your doctor will:

  • perform a physical examination of your baby
  • order a blood test called a karyotype to confirm Down syndrome

Treating Down Syndrome

There is no cure for Down syndrome, but there is also a wide variety of support and educational programs that can help both people with the condition and their families. The NDSS is just one place to look for programs nationwide.

Available programs start with interventions in infancy. Federal law requires that states offer therapy programs for qualifying families. In these programs, special education teachers and therapists will help your child learn:

  • sensory skills
  • social skills
  • self-help
  • motor skills
  • language and cognitive abilities

Children with Down syndrome often meet age-related milestones. However, they may learn more slowly than other children.

School is an important part of the life of a child with Down syndrome, regardless of intellectual ability. Public and private schools support people with Down syndrome and their families with integrated classrooms and special education opportunities. Schooling allows valuable socialization and helps students with Down syndrome build important life skills.

Living with Down Syndrome

Lifespan for people with Down syndrome has improved dramatically in recent decades. In 1960, a baby born with Down syndrome often didn’t see their 10th birthday. Today, life expectancy for people with Down syndrome has reached an average of 60.

If you are raising a child with Down syndrome, you will need a close relationship with medical professionals who understand the condition’s unique challenges. In addition to larger concerns, like heart defects and leukemia, people with Down syndrome may need to be guarded from common infections such as colds.

People with Down syndrome are living longer and richer lives than ever. Though they can often face a unique set of challenges, they can also overcome those obstacles in ways that inspire the rest of us. Building a strong support network of experienced professionals and understanding family and friends is crucial for the success of people with Down syndrome and their families. Check out the National Down Syndrome Society and the National Association for Down Syndrome for help and hope.

Read This Next

First Trimester Screening: What Will I Learn?
14 Things You Didn’t Know About Alzheimer’s
Signs of Low Testosterone in Men Under 30
Pregnant for the Holidays: 17 Holi-Yays and Holi-Nays
The Essential Stretches for Every Level of Gymnast