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Down syndrome is a congenital condition (present at birth) that occurs when a baby is born with three copies of chromosome 21 instead of two copies. It causes many specific physical characteristics and health complications.

The medical problems that are part of Down syndrome can cause disability and sometimes be life-threatening, but survival and quality of life are improving with advances in medical interventions.

This article explains the facts about Down syndrome, including how many people have it, risk factors, and screening.

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Overview of Down Syndrome

People born with Down syndrome, also called trisomy 21, have some notable traits and health issues.

The effects of Down syndrome include:

  • Small size, sometimes with subtle anatomical differences in the hands and feet
  • A characteristic appearance of the eyes and face
  • Skeletal malformations
  • Reduced hearing
  • heart defects
  • Pulmonary defects
  • weak immune system
  • Gastrointestinal malformations
  • Overweight or obesity
  • Learning delays or motor problems in some people
  • dementia praecox

All children born with Down syndrome develop one or more of these effects. However, many people with Down syndrome usually do not develop all the features.

How common is Down syndrome?

Down syndrome affects about one in 700 babies born in the United States, or about 6,000 live births per year. More than 200,000 people in the United States are currently living with this disease. The incidence of Down syndrome has remained stable in the population.

No therapy can prevent the effects of the extra chromosome if a child has it. But the overall health of people with Down syndrome improves with early detection and treatment of serious health conditions, such as heart disease.

The self-care abilities of people with Down syndrome have improved over the years through interventions such as physiotherapy and occupational therapy that can help people improve their mobility and maintain their independence.

Down syndrome by ethnicity

The physical effects of Down syndrome are the same regardless of ethnicity. Some aspects of Down syndrome management relate to access to care and lifestyle factors that may differ by ethnic group. This may affect the results.

For example, children who begin occupational therapy at a young age or who receive learning interventions in school may achieve greater independence than those who do not receive these interventions.

A small research study found that children with Down syndrome are more likely to be overweight or obese if their parents are not educated about the harmful health effects of obesity. In this small study, Hispanic/Latino boys with Down syndrome were more likely to be obese.

Down syndrome according to age and sex

The genetic differences that cause Down syndrome are present while a baby is still developing. The incidence is about the same for babies of all sexes. The developmental effects of Down syndrome begin in utero (before an affected baby is born).

Down syndrome cannot develop later in life – a person who does not have an extra copy of chromosome 21 in utero cannot develop an extra copy later. Additionally, Down syndrome is a lifelong condition that does not cure itself, and does not go away on its own.

Due to health effects and earlier than average risk of death, Down syndrome is more common in children than in adults, and the prevalence decreases with age.

Down syndrome causes and risk factors

Normally, a baby inherits two copies of each chromosome, one from each parent. Down syndrome occurs when a developing baby inherits three copies of chromosome 21 instead of two copies.

The extra chromosome can come from either parent. This happens due to a biological error called non-disjunction that affects the egg or the sperm that fertilized the egg.

Although anyone, regardless of age or background, can have a child with Down syndrome, there are certain risk factors. Risk factors include:

  • Advanced age of the parent contributing the egg and carrying the pregnancy is a known risk factor.
  • Having a sibling with Down syndrome is a risk factor.
  • Advanced age of the parent providing the sperm is a mild risk factor.

What are the death rates for Down syndrome?

There is substantial variation in survival with Down syndrome, and severe heart and lung defects are associated with poorer survival.

Some babies born with severe organic malformations may not survive beyond the age of one year, while children who have treatable malformations or who do not have significant organic malformations may survive much longer.

The most common causes of death for people with Down syndrome are heart disease, lung disease, infection, dementia, and cancer.

Average life

The average lifespan for someone with Down syndrome in the United States is approximately 55 years, which is compared to an overall average lifespan of 79 years in the United States.

Screening and early detection

The physical characteristics of Down syndrome may be noticeable at birth, but sometimes parents, healthcare providers, and others may not notice that a child has Down syndrome until they are a few years old. month or more. Also, parents and others may be more likely to notice that a child appears to have Down syndrome if there are risk factors.

Screening for Down syndrome includes testing during pregnancy.

Prenatal ultrasound

This non-invasive imaging test examines the baby’s physical characteristics and can visualize certain organic abnormalities associated with Down syndrome.

However, not all babies with Down syndrome have organic developmental abnormalities. This test may not detect abnormalities even if they are present, and some detected abnormalities could be caused by another developmental condition that is not Down syndrome.

Quad test

The quad test is a blood test that can be done after 15 weeks of pregnancy. It measures certain hormone levels that have been correlated with Down syndrome and other birth conditions. This test does not provide a definitive diagnosis of Down syndrome.


Amniocentesis take a sample of amniotic liquid (the fluid surrounding the fetus) for chromosomal analysis. It is the most definitive diagnostic test for Down syndrome. This can be done after the 15th week of pregnancy. This procedure has a very low risk of complications.


Screening is recommended for pregnant women aged 35 or older. It is also recommended for pregnant women under 35 who have had a child with Down syndrome.

Pregnant women are not required to be screened for Down syndrome. People at low risk can often request screening tests.


Down syndrome is a lifelong condition that occurs due to an extra copy of chromosome 21. This occurs due to a genetic error that affects either the egg or the sperm that fertilized the egg to produce the ‘child.

Down syndrome can cause many different physical problems, including abnormal musculoskeletal development, heart defects, digestive problems, learning disabilities, and more. It is a lifelong disease that can lead to disabilities. Often, medical and practical interventions can lessen some of the effects and improve quality of life.

Frequently Asked Questions

  • Is Down syndrome hereditary?

    Most people with Down syndrome have no family history of the disease. Down syndrome is caused by a parental chromosomal abnormality, but it affects the child and not the parents. If a person with Down syndrome has a child, that child will have a 1 in 2 chance of inheriting Down syndrome.

  • When can Down syndrome be diagnosed?

    Down syndrome can be diagnosed early in pregnancy with a chromosome test by amniocentesis. Amniocentesis is a procedure in which a sample of fluid is taken from a pregnant person. The sample would be examined in a lab and the results would show if a baby had any genetic abnormalities, such as three copies of chromosome 21.

  • Do all people with Down syndrome have the same physical and learning limitations?

    Certain physical characteristics and health problems occur as a result of an extra copy of chromosome 21, but the effects may be slightly different for each person.

    For example, some people with Down syndrome may have severe heart defects, while others may have mild heart damage. The type of malformations of each person can differ.

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