Today is International Down Syndrome Day.

World Down Syndrome Day (WDSD), celebrated on March 21, is a United Nations-recognized global awareness day since 2012. To celebrate WDSD, we will talk more about Down syndrome.

How is Down syndrome defined?

Down syndrome is a genetic condition in which an individual is born with an extra chromosome. Chromosomes are the small “packages” of genes in the body. They influence the way a baby’s body develops and functions during pregnancy and after delivery. A baby is usually born with 46 chromosomes. Babies with Down syndrome are born with an extra copy of one of these chromosomes, chromosome 21.

Trisomy is a medical word for having an extra copy of a chromosome. Trisomy 21 is another term for Down syndrome. This extra copy changes the way the baby’s body and brain develop, posing mental and physical obstacles for the infant. Although people with Down syndrome may act and appear similarly, each individual has unique abilities. People with Down syndrome typically have a mild to moderately low IQ (intelligence quotient) and speak more slowly than other children.

What are the signs of Down syndrome?

Several common physical characteristics of Down syndrome include the following:

  • A flattened face, especially the bridge of the nose
  • Almond eyes that tilt
  • A short neck
  • Small ears
  • A tongue that tends to stick out of the mouth
  • Tiny white spots on the iris (colored part) of the eye
  • Little hands and feet
  • A single line on the palm of the hand (palmar crease)
  • Tiny pink fingers that sometimes curve towards the thumb
  • Poor muscle tone or loose joints
  • Smaller in size than children and adults

How common is Down syndrome?

Down syndrome continues to be the most commonly diagnosed chromosomal disorder worldwide. About two out of every 1,000 babies born each year in South Africa have Down syndrome.

Down syndrome has several subtypes

Down syndrome is classified into three subtypes. Since the physical characteristics and behaviors of each type are generally identical, people often cannot determine the difference between them without examining the chromosomes.

Trisomy 21 : About 95% of people with Down syndrome have trisomy 21. In this type of Down syndrome, each cell in the body contains three separate copies of chromosome 21 instead of the usual two.

Down syndrome by translocation: This subtype accounts for a relatively small proportion of people with Down syndrome (about 3%). This occurs when an extra part or an entire chromosome 21 is present, but it is connected or “translocated” to another chromosome rather than being a separate chromosome 21.

Mosaic Down Syndrome: About 2% of people with Down syndrome have this form. Mosaic is a term that refers to a mixture or a combination. Children with mosaic Down syndrome have some cells with three copies of chromosome 21, while others have the standard two copies. People with mosaic Down syndrome may have the same characteristics as other children with Down syndrome. They may, however, show fewer features of the disease due to the presence of some (or more) cells with a normal number of chromosomes.

Causal factors and risk factors

The extra chromosome 21 causes the physical characteristics and developmental difficulties associated with Down syndrome. While researchers are convinced that an extra chromosome causes Down syndrome, no one knows exactly why it occurs or how many separate factors contribute to it.

The age of the mother is a factor that increases the likelihood of having a child with Down syndrome. Women who get pregnant at age 35 or older are more likely to have a pregnancy affected by Down syndrome than women who get pregnant at a younger age. However, most babies born with Down syndrome are to mothers under the age of 35 due to the higher birth rate among younger women.


Two tests are available to detect Down syndrome during pregnancy: screening tests and diagnostic tests. A screening test can tell a woman and her health care provider whether her pregnancy has Down syndrome.

Although screening tests cannot provide a definitive diagnosis, they are much safer for the mother and developing infant. Although diagnostic tests can often determine whether or not a baby will have Down syndrome, they can be more dangerous for the mother and growing infant. Neither screening nor diagnostic techniques can accurately predict the full impact of Down syndrome on a baby; nobody can.

Often, screening tests combine a blood test to determine the presence of several compounds in the mother’s blood with an ultrasound to create an image of the baby. Fluid behind the baby’s neck is one of the things the technician looks for during an ultrasound. Extra fluid there may suggest a genetic problem. These screening tests can help determine if a baby is at risk for Down syndrome.

Sometimes screening tests will produce an abnormal result even though the infant is perfectly healthy. Sometimes test results are normal but fail to detect an underlying problem. Diagnostic tests are usually ordered following a positive screening test to confirm the diagnosis of Down syndrome. These tests check for chromosomal abnormalities that would imply a diagnosis of Down syndrome.

Additional health issues

Many people with Down syndrome share the same facial features and have no other significant birth defects. However, some people with Down syndrome may have one or more significant birth defects or other medical complications. Here are some of the most common health problems experienced by children with Down syndrome:

  • Hearing impairment
  • Obstructive sleep apnea (a condition in which a person’s breathing momentarily stops during sleep)
  • ear infections
  • Eye diseases
  • Congenital heart defects


Down syndrome is a chronic disorder that requires lifelong care. Early intervention services frequently help infants and children with Down syndrome develop their physical and intellectual abilities. The majority of these services aim to help children with Down syndrome reach their full potential.

These treatments, including speech therapy, occupational therapy, and physical therapy, are typically provided through each state’s early intervention programs. Children with Down syndrome may also need more assistance or attention at school, but many are integrated into mainstream schools and educational platforms.

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