When a baby is born with an extra copy of chromosome 21, it alters how their brain and body develop. This can cause mental, physical and societal challenges. Understanding Down syndrome can help you make decisions about your pregnancy and be better prepared for the birth.
What is Down Syndrome?
Down syndrome, also known as Trisomy 21, is a genetic condition in which a child is born with an extra chromosome.- Most people, in general, are born with 23 pairs of chromosomes in each cell of their bodies, leading to a total of 46 chromosomes.
- A child diagnosed with Down syndrome has an extra copy of chromosome 21, which means their cells have 47 chromosomes instead of 46.
- This affects the way they develop and causes a lot of mental and physical changes. Children diagnosed with Down syndrome often face developmental challenges.
Genetic Basis of Down Syndrome
People with Down syndrome have the same genes as anyone else. They just have an extra chromosome.- The extra copy of chromosome 21 can be caused by an error during the formation of the egg or the sperm cell, which leads to the egg and sperm each having an extra chromosome.
- When the egg and the sperm cells unite, the resulting cell has three copies of chromosome 21.
- In rare cases, Down syndrome can occur when a part of chromosome 21 becomes attached to another chromosome while reproductive cells are forming or during early foetal development.
Types of Down Syndrome
There are three distinct types of Down syndrome, based on how the extra chromosome is present in a child’s cell.- Trisomy 21: Trisomy 21 is the most common type of Down syndrome, and it affects about 95% of the people who have Down syndrome. In this type, every cell of the body has an extra copy of chromosome 21.
- Translocation Down Syndrome: This type affects about 3% of the people who have Down syndrome. This occurs when an extra or partial copy of chromosome 21 attaches itself to another chromosome, instead of being a separate chromosome.
- Mosaic Down Syndrome: This affects about 2% of the people who have Down syndrome. This type of Down syndrome is caused by a random event that occurs shortly after the egg and the sperm join. While the cells are dividing, some cells receive an extra copy of chromosome 21, while others do not. There is no way of knowing which cells have the extra chromosome.
Down syndrome and Its Risk Factors
Down’s syndrome can happen to anyone. It is a genetic condition and does not happen because of the actions of the parents during or before pregnancy. Most Down syndrome cases occur randomly. People do not inherit Down syndrome. However, there are some risk factors that might contribute to Down syndrome.- Mother’s age: The risk of having a baby with Down syndrome increases with the woman’s age. A woman who is above 35 years of age is more likely to give birth to a baby with Down syndrome than a woman who is 29. The risk increases even further for women who are 40 or above.
- Family history: Usually, Down syndrome is not inherited. It does not run in families. However, in about 3-4% of cases, Down syndrome is caused by translocation, which happens when genetic material from chromosome 21 is rearranged onto another chromosome. In about one-third of the cases, a parent is the carrier of this translocated chromosome. If you have a family history of Down syndrome, you can speak to your doctor about your risk of having a baby with Down syndrome. Less than 1% of Down syndrome cases have a familial connection.
- Previous child with Down syndrome: If you already have a child with Down’s syndrome, you might be concerned about your chances of having another child who has Down syndrome. However, the risk of having a second child with Down syndrome is only 1% for couples who have one child with the condition.
- Genetic translocation: There is a 3% risk of recurrence of translocation if the father is the carrier. This risk increases to 10-15% if the mother is the carrier.
How is Down Syndrome Diagnosed
Down syndrome is diagnosed with the help of prenatal screening tests and diagnostic tests. Both of these are essential for early detection of Down syndrome. While both of them help with the detection of the condition, they both have different purposes and levels of accuracy.Screening Tests:
Screening tests do not provide a definitive diagnosis. They can only predict the likelihood of having a foetus with Down syndrome.
- Nuchal Translucency Test: The Nuchal Translucency Test (NT Test) is done between the 11th and 14th weeks of pregnancy. It measures the amount of fluid at the back of the baby’s neck. An increased amount of fluid can indicate chances of Down syndrome.
- Blood Test: Blood tests done in the first trimester can test the mother’s blood and check if the foetus’s DNA has traces of chromosomal abnormalities. A blood test called the Karyotype test can identify and analyse a baby’s chromosomes to look for an extra copy of chromosome 21 and diagnose Down syndrome.
Diagnostic Tests:
Diagnostic tests are much more accurate and can provide you with a definitive answer on whether your child has Down syndrome. These tests directly analyse the foetus’s chromosomes.
- Amniocentesis: This test is done between the 15th and 20th weeks of pregnancy. The doctor takes a small sample of amniotic fluid from your uterus using a needle, and the foetal cells in the sample are tested for chromosomal abnormalities.
- Chorionic Villus Sampling (CVS): This test is done between the 10th and 13th weeks of pregnancy. For this test, a sample of your placenta is taken to conduct genetic tests on
Since diagnostic tests are invasive and carry a small chance of miscarriage with them, they are only recommended if the initial screening indicates a risk of Down syndrome.
Impact of Down Syndrome
Down syndrome has a huge impact on both the baby and the parents. It can be a life-changing diagnosis. Here are some ways that Down syndrome can emotionally and physically alter lives.- Developmental challenges: People with Down syndrome may face developmental challenges and delays, such as learning to walk, speak and eat, on their own much later.
- Cognitive and behavioural issues: People with Down syndrome may face mild to moderate cognitive and emotional impairment. This includes cognitive and behavioural issues such as impulsive behaviour, poor judgement, and short attention span.
- Health challenges: People who have Down syndrome have a higher risk of developing health conditions, such as vision impairment, heart conditions and hearing loss. They also have a higher chance of developing blood disorders like anaemia.
Physical Characteristics of Babies with Down Syndrome
- Flattened face, especially from the bridge of the nose and a protruding tongue
- Almond-shaped eyes that slant up, with white spots at the coloured parts of the eye, called Brushfield spots
- Small ears, folding over the top
- Wide, short hands with short fingers and a small crease over the palm
- Small feet with a wide gap between the first and second toes
- Short neck, with excessive skin at the back of the neck
- Shorter than average height
- Poor muscle tone and joints
Early Intervention and Support Systems
To promote their development and potential, early intervention methods are crucial for children born with Down syndrome. Therapies like speech, physical, occupational, and behavioural therapies can be beneficial to the child’s progress.When it comes to education, it is best to look for educational programmes designed for children with special needs, and programmes that are inclusive.
Parents of children with Down syndrome have several support groups and online communities. Connecting with other parents with similar life journeys can enrich your own.
Long-term Care and Life Expectancy
Earlier, the life expectancy for people with Down syndrome was not as high as it is today. This is largely due to medical advancements. People with Down syndrome can live fruitful lives well into their 60s and beyond. Medical advancements today have made it possible to get better treatments for heart defects and other issues associated with Down syndrome.Getting regular medical tests done and continuing therapy is a key part of long-term care for Down syndrome.
Common Misconceptions About Down Syndrome
- Myth: People with Down syndrome have a short lifespan:
- Myth: Down syndrome is rare:
- Myth: People with Down syndrome have severe intellectual disabilities:
- Myth: Down syndrome is hereditary:
It is important to get screened for chromosomal abnormalities early in your pregnancy so that you are better prepared for any complications. If your child is diagnosed with Down syndrome, it would be best for you to do further research on the condition to understand it better. There are a lot of myths and misconceptions associated with the condition. Understanding these, and creating an open, safe space for your child is the best way to help them develop and progress for the world.
FAQs on Understanding Down Syndrome And Its Risk Factors
- What is the main cause of Down syndrome?
Down syndrome is caused by a random error in the division of cells that leads to an extra copy of chromosome 21. - What increases the risk of Down syndrome?
Down syndrome is a chromosomal abnormality that can happen to anyone, however, the mother’s age seems to have some role to play. Pregnancies that occur over the age of 35 have a higher chance of delivering a baby with Down syndrome. - What are some health risks associated with Down syndrome?
People who have Down syndrome have a higher risk of developing vision impairment, hearing difficulties and heart anomalies later in life.
