In South Africa, 1 in 500 children are born with Down Syndrome every year – Let’s take a closer look at the most common genetic chromosomal disorder and leading cause of intellectual disability in children.
Each cell in our body has 23 pairs of chromosomes – so 46 chromosomes in total. Chromosomes contain the genetic material that make you YOU! The only cells in our body that don’t have 46 chromosomes are the eggs in females and the sperm in males – these contain 23 each. So when the egg and sperm meet, the 23 from the egg combine with the 23 from the sperm and make a new person with 46 chromosomes. A person with Down Syndrome has an extra chromosome 21, giving them a total of 47 chromosomes – and this is what makes them different.
So how does this happen?
The extra chromosome occurs when cells divide abnormally either during development of the egg or sperm cell, or during fertilization. It is rare for Down Syndrome to be inherited (passed down from parent to child) – it is mostly a random mistake of cell division.
What increases the risk of having a child with Down Syndrome?
A major factor is the age of the mother – the older the mom, the higher the risk. This is because as you age the chances of abnormal cell division happening is higher. At age 35 a woman’s risk of having a Down Syndrome child is about 1 in 350 and by the age of 45 it is 1 in 30.
People affected by Down Syndrome can have a range of features and issues – from mild to severe. Typically there are distinctive facial features, poor muscle tone, intellectual disability and short stature. Other issues can include heart defects, increased risk of leukaemia and infections (due to a weak immune system), and a high risk of dementia.
Prenatal screening for Down Syndrome can be done – many low risk women choose to be screened and those at high risk will be urged to do undergo screening by their doctor. Screening involves a number of investigations such as specialised ultrasounds and blood tests done in the first trimester of pregnancy. If screening picks up that there may be an issue further diagnostic tests are done which are more invasive. It is important to note though that Down Syndrome is not necessarily an indication to terminate a pregnancy – and before you have any screening tests done you need to be prepared to deal with decisions that you may have to make down the line. Women often choose not to be screened as they would not consider termination even if their baby was thought to have Down Syndrome.
Many people with Down syndrome go on to live fulfilling lives – able to live independently, go to mainstream schools and find jobs. This can be done if there is early intervention from doctors, other health care providers, teachers, therapists and of course by having a strong support group of family and friends. This week is Down Syndrome Awareness week so let’s support Down Syndrome South Africa and their “IT’S ALL IN THE GENES” campaign on the 20th October by wearing our JEANS and donating R5 to the organisation (have a look at www.downsydrome.org.za for more info and how you can help).
Author: Dr Lynelle Hoeks