Are you a mother-to-be? Or are you planning to become one soon? Then today we will talk about some special tests that will help you learn more about the health of you and your unborn baby. These are what we call 'genetic testing '. Most of these tests are not mandatory, but the information they provide can be a great help in planning for the future for you and your family.
Before pregnancy: Genetic Carrier Screening
To put it simply, let's first look at who is a 'carrier'. Imagine that you have a gene for a certain disease in your genes, but you don't have the disease. Then you are called a 'carrier'. So, this test can tell you whether you and your partner carry the gene for a certain disease, and if so, what is the likelihood that your child will inherit that gene.
Although this test can be done before or during pregnancy, it is most useful to do it before pregnancy. Your doctor will take a blood sample or a saliva sample from you to perform this test. There are several main conditions that are usually screened for with this test.
| Main genetic conditions tested for |
|---|
| Cystic Fibrosis |
| Fragile X Syndrome |
| Sickle Cell Disease |
| Tay-Sachs Disease |
| Spinal Muscular Atrophy |
Some ethnic groups are more likely to be carriers of certain diseases. For example, people of African, Mediterranean, and Southeast Asian descent are more likely to be carriers of sickle cell disease. So, talk to your doctor about your family history and decide if you need to be tested for this condition.
Tests during the first trimester (within 3 months) of pregnancy
Once you're pregnant, there are several tests that can help you find out about your baby's health risks. These are called screening tests . They only look at whether you're at 'risk' for a certain disease.
- Cell-free fetal DNA testing: Amazingly, your blood contains small amounts of your baby's DNA. So, around 10 weeks into your pregnancy, a blood sample taken from you can be used to test your baby's DNA to see if you're at risk for certain conditions (e.g., Down syndrome, trisomy 18, trisomy 13).
- Sequential screen and Integrated screening: Both of these methods combine an ultrasound scan and a blood test to check for Down syndrome, trisomy 18, and other problems that can affect the baby's brain and spinal cord. These tests are started between 10 and 13 weeks .
The important thing is that these are only screening tests. If they indicate that there may be a problem, your doctor will recommend other specific tests to confirm it.
Tests performed in the second trimester (between 3-6 months)
There are several important tests at this stage of pregnancy.
- Maternal serum quad screen: This is also a blood test. It measures several types of proteins in your blood to see if your baby is at risk for Down syndrome , trisomy 18, or brain and spinal cord problems. This can be done between 15 and 21 weeks .
- Detailed Ultrasound Scan (Anomaly Scan): This scan, which is done around 20 weeks, is probably familiar to most people. It uses sound waves to examine the baby's organs. It can detect birth defects such as heart problems, kidney problems, and cleft palate.
Diagnostic Tests: Amniocentesis and CVS
If a screening test shows that the baby is at risk, these are the tests that are done to confirm it 100% . These are more accurate than screening tests. These are called Diagnostic Tests.
Both of these tests are more than 99% accurate.
These tests can accurately identify genetic conditions like Down syndrome. But not everyone does these tests. Because, although very small, there is a risk of miscarriage with these tests. Therefore, the doctor only suggests these if a screening test indicates a risk, or if you want to have a more accurate test.
| Test | How to do it and when |
|---|---|
| Chorionic Villus Sampling (CVS) | A very small piece of tissue is taken from the placenta in the uterus. This is done between 10 and 13 weeks . |
| Amniocentesis | A small amount of amniotic fluid is removed through your abdomen using a thin needle. This is safest done between 15 and 20 weeks . |
If your doctor tells you about this type of test, it doesn't mean that there is definitely a problem with your baby. It just means that they need to confirm the results of a previous screening test. So, talk to your doctor about it carefully, understand the pros and cons, and make the decision that's right for you.
Take-Home Message
- Most of these genetic tests are optional, not mandatory, tests that you can choose from.
- Screening tests (e.g. Cell-free DNA, Quad screen) only indicate the risk of a disease, while diagnostic tests (e.g. Amniocentesis, CVS) definitively confirm a disease.
- If a screening test result is risky, it doesn't mean your baby definitely has a problem. It's just a reason to seek further testing.
- Each test has unique benefits, disadvantages, and risks. It's important to discuss all of these openly with your doctor and make an informed decision.
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