In this article, we help you understand who should consider this and when, along with the different kinds of tests and what to do with those results.
When Should You Consider This?
Some genetic tests can be done when you start family planning to detect any genetic conditions already present in both parents. This is called preconception genetic testing. Sometimes, one or both parents can be carriers for a genetic disorder while not having the condition themselves. This way, this faulty gene can be passed to their future children and increase their risk of developing it.
These tests can also be performed once you conceive. We call this prenatal genetic testing. At this stage, we can test both the parents as well as the unborn baby, which gives us a better picture of the possible genetic abnormalities or birth defects the child could potentially have.
Results at both these stages help us decide the next course of action.
Why Should You Consider This?
Genetic testing can help us assess the risk and even diagnose inherited genetic disorders, chromosomal abnormalities and birth defects before or during the pregnancy.
It's important to note that these tests are strictly regulated by the Pre-Conception & Pre-Natal Diagnostic Techniques Act (PCPNDT), 1944. This act ensures that these tests are only used to detect disorders and defects in the unborn child and not for sex determination.
Sex determination is illegal in India, and all hospitals, clinics and laboratories have to comply with this law.
Who Should Consider This?
Genetic testing is not compulsory for all, but is encouraged for expectant parents. Doctors and genetic counsellors especially advise these tests for high-risk cases, such as:
- Maternal age above 35 years (as it increases the risk of conceiving a child with Down syndrome).
- Personal or family history of genetic disorders on either side of the family.
- History of conceiving or giving birth to a child with a genetic disorder or birth defect in a previous pregnancy.
- History of stillbirth or miscarriage.
- Abnormal findings in a routine ultrasound checkup.
- Consanguineous relationships (marriage between close relatives can cause abnormalities in future children)
Types of Tests
There are two types of genetic tests with different purposes:
- Screening Tests: These tests help in determining the risk of a genetic disorder or defect in your future offspring. However, they can't confirm or diagnose the condition.
The different types of screening tests are as follows:
- Carrier Screening: This is a type of blood test done in couples only once in their lifetime. It helps to figure out if you or your partner carries genes for any genetic disorders.
- Abnormal Chromosome Number: Normally, the child inherits one-half of the chromosomes from each parent to form a pair.
But sometimes, this process malfunctions, resulting in an extra (Down Syndrome) or missing (Turner’s Syndrome) part of the chromosome pair.
The results for these tests can be different for each pregnancy. The abnormalities in chromosome number can be assessed by two tests:
- Cell-Free Foetal DNA Screening/Non-Invasive Prenatal Testing (NIPT):
Here, foetal DNA present in small amounts in the mother's blood is evaluated for abnormal chromosome number. This test is performed in the first trimester after 10 weeks of pregnancy.
- Serum Screening:
Here, the maternal blood sample is tested for various protein levels to find any abnormalities. This test is performed after 11 weeks of pregnancy.
- Screening for Physical Abnormalities:
Here is a list of tests that can be done to look for any possible physical defects in the unborn child:
- Nuchal Translucency:
An ultrasound is done to measure the thickness of the back of the baby's neck in the womb. A thick neck indicates physical deformities like heart defects. This test is performed between 11 and 14 weeks.
- AFP (Alpha-Fetoprotein) Screening:
High levels of AFP in the maternal blood sample indicated spine, face or abdomen defects. Performed between 15 and 22 weeks.
- Quad Screen/Multiple Marker Screen:
The levels of four substances are measured in the maternal blood to assess any abnormalities. Performed between 15 and 22 weeks.
- Foetal Anomaly Scan:
An ultrasound is done to evaluate the baby's face, arms, legs, abdomen, spine, heart and kidneys in the womb. Performed between 18 and 20 weeks.
2. Diagnostic Tests: These tests are only advised by doctors if a screening test result is abnormal or in high-risk cases.
- Amniocentesis:
Performed between 16 and 22 weeks.
- Chorionic Villus Sampling (CVS):
Genetic Counselling After Testing
This process of testing is often overwhelming, especially if the test results render bad news. Genetic counsellors are trained specialists who help you navigate the results and help you understand your options.
Counselling after test results can help with:
- They listen to you and your partner’s medical history and advise tests on the basis of that.
- They help you understand the benefits and risks of these tests.
- Interpreting screening test results and understanding the risk.
- They might even advise diagnostic tests in high-risk cases.
- Once you receive the test results, they will help in understanding your options.
- In severe cases, they might even advise terminating the pregnancy and recommend alternate ways like IVF, adoption and more.
- They help you plan and prepare for a child with special needs.
- They offer significant emotional support during this process and even refer to other specialists if needed.
Genetic testing and counselling are still not mainstream in most pregnancies due to a lack of awareness. But it can be a real game changer in navigating complex conditions even before your child is born, and make you better prepared as a parent.
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FAQs on Prenatal Genetic Testing Explained: What Parents Should Know Before Birth
- Are there any side effects of doing genetic tests during pregnancy?
There are usually no risks associated with screening tests, as they are primarily done using maternal blood samples. However, there is a very slight risk of miscarriage, infection of the uterus, leakage of amniotic fluid or light bleeding after invasive procedures such as amniocentesis or CVS. You can discuss these potential risks with your healthcare provider before the tests. - Are the test results always accurate?
Even though screening tests are mostly accurate, sometimes the results may be false positives (the test result is high risk for a condition, but the baby might be healthy), false negatives (the test result shows low risk for a condition, but the baby might actually have it) or inconclusive. - My father has a genetic heart condition, but I don't have it. Can my child still get this condition?
Yes, it is possible that even if you don't have the condition, your future children might still get it. This happens because even though the condition didn't manifest in you, you might still carry the gene causing this, and your child might inherit the gene. This risk further increases if your partner also carries this gene. To rule this out, you and your partner can get a carrier screening test done.
