What is Down Syndrome?
In the United States, Down syndrome (also known as trisomy 21) is the most frequent chromosomal disorder. A chromosomal condition (also known as a genetic disorder) occurs when one or more chromosomes are damaged. The structures that hold genes are known as chromosomes. Genes are instructions for how your body grows and works that are stored in the cells of your body. Genes are passed from generation to generation.
Down syndrome affects about one out of every 700 infants (less than 1%). Many Down syndrome youngsters enjoy healthy, busy lives. They can attend school, participate in activities, and socialise with others. A person with Down syndrome has a chance of living for 60 years or longer.
What causes Down syndrome?
Each person contains 46 chromosomes, which are divided into 23 pairs. You acquire one chromosome from your mother and one from your father for each pair. Down syndrome babies have an extra copy of chromosome 21. The brain and body develop differently as a result of the extra copy.
We don’t know exactly why Down syndrome develops. The egg or sperm that fertilise each other may have an additional chromosome. When a man’s sperm enters a woman’s egg, this is called fertilisation. This is how a woman conceives.
These factors may influence your chances of having a child with Down syndrome:
- Your age when you get pregnant: As you become older, your chances of having a baby with Down syndrome increase, especially if you’re 35 or older.
- Being a carrier of a certain type of Down syndrome: You or your partner can carry (have) a genetic alteration for one type of Down syndrome (Down syndrome with translocation), but you do not have the condition. It is possible to pass the genetic alteration to your child, although this is rare.
- Already having a baby with Down syndrome: If you already have a Down syndrome child, your chances of having another are increased.
Consult a genetic counsellor to learn more about your chances of having a child with Down syndrome. A genetic counsellor is someone who has been trained to assist you to understand how genes, birth abnormalities, and other medical disorders that run in families can affect your health and the health of your baby.
What are the different types of Down syndrome?
There are three types of Down syndrome:
- Trisomy 21: This is the most typical type. Trisomy 21 is present in about 95% of people with Down syndrome. Your baby’s cells have three copies of chromosome 21 instead of two in this situation.
- Translocation Down syndrome: Translocation Down syndrome affects about 3 out of 100 people with Down syndrome (3%). When a person has two copies of chromosome 21 but also has an extra fragment of chromosome 21 or a full extra chromosome 21 attached (also known as translocated) to a different chromosome, they have this disease. Down syndrome with translocation can be inherited (passed from parent to child through genes).
- Mosaic Down syndrome: Mosaic Down syndrome affects about 2 out of every 100 people with Down syndrome (2%). Some cells in people with this syndrome contain three copies of chromosome 21, whereas others only have two copies. Because they have some cells with two copies of chromosome 21, people with mosaic Down syndrome may have fewer Down syndrome symptoms.
Is it possible to know if your baby has Down syndrome during pregnancy?
Yes. As part of routine prenatal care, health care workers test all pregnant women for Down syndrome (medical care you get during pregnancy). You can choose whether or not to take these tests. If you want to be tested for Down syndrome, go to your doctor or a genetic counsellor.
See your doctor if you or your life partner has a family history of Down’s syndrome. If you have a family history of the disease, it indicates that someone in one of your families has it. To see if specific health disorders run in your family, fill out our family health history form.
To check for Down syndrome, there are two types of prenatal tests:
- Screening tests: These are medical tests that determine whether you or your baby are at risk for certain health problems. A Down syndrome screening test determines whether your baby is more likely to have Down syndrome than other newborns. Screening tests are completely safe for both you and your baby during pregnancy, but they will not tell you if your baby has a condition like Down syndrome.
- Diagnostic tests: These are medical tests that determine whether or not you have a certain health issue. Diagnostic testing may carry higher risks than screening tests, but they can definitively determine whether or not your baby has Down syndrome. If a screening test indicates that your baby has a high risk of Down syndrome, your doctor may suggest a diagnostic test to confirm the findings.
The findings of a screening test can help you decide whether or not you need a diagnostic test. It is entirely up to you whether or not you wish to undergo diagnostic tests. You may or may not want to know if your baby has Down syndrome during pregnancy. If you find out for sure, you can study more about the condition so you’ll be ready for your baby’s arrival. You can also make arrangements for any medical care your baby may require.
Screening tests for Down syndrome include:
- First-trimester screening. These tests are used by your provider to determine whether or not your baby is at risk for Down syndrome or other birth abnormalities. At 10 to 13 weeks of pregnancy, a test is routinely performed. There are two sections to it:
- Blood test. This test looks at the amounts of two proteins in your blood: plasma protein-A (also known as PAPP-A) and human chorionic gonadotropin, a pregnancy hormone (also called HCG). Your infant may be at risk for Down syndrome if these values are abnormally high or low.
- Nuchal translucency test: This ultrasound is used to check for excess fluid in your baby’s neck. An ultrasound shows an image of your baby within the womb using sound waves and a computer screen. Extra fluid could put you at risk for Down syndrome.
- Second-trimester screening: You have a maternal blood test (also known as a quad screen) to check for alpha-fetoprotein (AFP), estriol, HCG, and inhibin A, which can indicate an increased chance of Down syndrome. A triple screen is a test that measures three of these proteins, while a quad screen is a test that measures four of these proteins. The test is typically performed between 15 and 22 weeks of pregnancy.
- Integrated screening test. To better predict the likelihood that your baby has Down syndrome, your provider combines the findings of the first-trimester screening and the second-trimester screening.
- Cell-free DNA testing (also called noninvasive prenatal screening or testing or NIPT). This test looks for your baby’s DNA in your blood to discover if he has a higher risk of Down syndrome. This test can be done as early as 10 weeks into your pregnancy. Consult your healthcare physician to see if this test is appropriate for you.
A diagnostic test involves taking a sample of your baby’s blood, amniotic fluid, or tissue for testing with a needle. These diagnostic tests carry a minor risk of miscarriage. Miscarriage is the loss of a baby before the 20th week of pregnancy.
The following tests can be used to diagnose Down syndrome:
- Chorionic villus sampling (also called CVS): This test examines placental tissue to detect if your baby has a genetic problem such as Down syndrome. CVS can occur anywhere between 10 and 13 weeks of pregnancy.
- Amniocentesis (also called amnio): This test examines the amniotic fluid surrounding your baby in the uterus (womb) for birth abnormalities and genetic problems. This test is available between 15 and 20 weeks of pregnancy.
- Percutaneous umbilical cord sampling (also called PUBS or cordocentesis): This test checks for chromosome problems by drawing a little amount of blood from your baby’s umbilical cord. This test is available between 18 and 22 weeks of pregnancy. Because the risks of PUBS are higher than those of amnio or CVS, you should only have it if the results of other tests are inconclusive and you want to confirm whether or not your baby has Down syndrome.
How are babies with Down syndrome diagnosed after birth?
Your baby’s provider offers him or her a medical exam after birth, looking for physical signs of Down syndrome. She sends a sample of your baby’s blood to a lab for testing to confirm whether or not your baby has Down syndrome.
What are the physical characteristics of a person with Down’s syndrome?
A person with Down syndrome may have a variety of physical traits, such as:
- Facial features. The majority of Down syndrome babies exhibit some of the following characteristics:
- A smallmouth
- A flattened face, with a flat nose.
- A tongue sticking out of the mouth
- Almond-shaped eyes that slant upward
- Small white spots on the iris (coloured part) of the eye
- Other physical characteristics. Some of the following traits may be present in babies and children with Down syndrome:
- Small ears
- A short neck
- Short height
- Hypotonia (low muscle tone) or loose joints
- A single line on the palm of the center of the hand (also called the palmar crease)
- The hands and feet are small. They may also have short little fingers that curve towards the thumb at times.
How does it affect your child’s health and development?
Although many people with Down syndrome are healthy, some require specialised medical attention. The following are some of the most common health and development issues that people with Down syndrome face:
- Hearing loss
- Dental problems
- Eyesight problems
- Blood disorders
- Congenital heart defects
- Low muscle tone
- Hip problems
- Thyroid problems
- Intellectual and developmental disabilities
- Neck or spine problems
- Sleep disorders, such as obstructive sleep apnea
- Problems with digestion and intestines, such as Hirschsprung’s disease.
- Emotional and mental health problems