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What Is Genetic Testing During Pregnancy?
Genetic testing during pregnancy can help determine whether or not the baby has a genetic condition. There are several sorts of genetic tests available, each providing distinct information.Prenatal Genetic Testing Vs Preconception Genetic Testing
Prenatal genetic testing and preconception genetic testing are done before the baby is born. However, preconception genetic testing, also known as carrier screening is done before conception.Carrier screenings examine parents to see if they are carriers of specific genetic illnesses, according to Dr Sunita Nagpal, General Physician, at Salubritas Medcentre.
This information can help doctors determine a couple's risk of having a child with a genetic condition if and when they become pregnant. Prenatal genetic testing, on the other hand, is performed after the baby has been conceived; these screenings determine the infant's genetic makeup.
Types of Genetic Tests During Pregnancy
Prenatal genetic testing is a broad phrase that includes both genetic screening and diagnostic tests. While both types of tests look for specific genetic markers, they differ significantly in how they are performed and what the results signify.Genetic Screening Tests
Several sorts of tests can be performed at different stages of pregnancy. The process begins with a genetic screening test that measures the likelihood of a genetic condition. The test does not provide diagnostic information about the baby's health or well-being. In other words, they can predict the presence of a problem but cannot confirm its existence.The results of these tests can be misleading, according to experts. While the terminology of 'positive' or 'negative' is often used on genetic screening reports, it would be much more appropriate to read as 'increased risk', followed by a probability, or 'decreased risk', followed by a probability. Essentially, the results of these tests are not definite, but they might help parents determine whether they want to pursue more testing for more conclusive answers.
Prenatal genetic screening tests may include:
First-trimester screening
According to the experts, this is done between 10 and 13 weeks of pregnancy and comprises a blood test and nuchal translucency screening ultrasound. The results of both tests are combined to assess the risk of Down syndrome, other chromosomal abnormalities, and potential heart, bone, and/or abdominal wall issues.Second-trimester screening
This is another two-part test, consisting of a blood test and an ultrasound. The blood test, which can be performed between 15 and 22 weeks of pregnancy, checks for the risk of Down syndrome, Edwards syndrome, and neural tube abnormalities (NTD). The ultrasound is performed between weeks 18 and 22 of pregnancy and looks for abnormalities in the baby's limbs, heart, brain, spine, abdomen, and facial features.Screening during both the first and second trimesters
According to the journal Understanding Genetics, this is sometimes referred to as an "integrated" screening; it occurs when the results of all four screening tests are combined with factors such as a mother's age and weight to produce slightly more accurate screening results. This test is done during the first and second-trimester and the findings of a combination screening are not accessible until 18 to 22 weeks gestation.DNA testing in the absence of living cells
This blood test, also known as noninvasive prenatal testing (NIPT), can be administered as early as 10 weeks of pregnancy. It extracts the baby's DNA from the mother's blood and screens for Down syndrome, Patau syndrome, Edwards syndrome, and chromosomal abnormalities.Again, it's crucial to note that these screens simply offer parents an indication of their baby's probability of developing these genetic illnesses; there is no certainty in a "positive" or "negative" result. At this stage, parents can choose to accept their results and discontinue genetic testing, or they can proceed with diagnostic testing.
Diagnostic Genetic Tests
A diagnostic test is a direct test of the cells from the pregnancy and can determine with a high level of accuracy whether a pregnancy is affected by a genetic condition.Diagnostic testing differs from prenatal genetic screenings not only in terms of accuracy but also in terms of invasiveness. Furthermore, unlike screenings, which are performed during a routine prenatal exam, diagnostic tests are performed by an expert, often outside of your ob-gyn office.
There are two types of diagnostic genetic testing, both with a low risk of miscarriage.
The testing options are:
Amniocentesis
This type of diagnostic test can be conducted at any time after the 15th week of pregnancy and has a 99.9 per cent accuracy rate in predicting whether the baby has a chromosomal genetic disorder, such as Down syndrome. According to the experts, this approach can also be used to screen for neural tube defects like spina bifida and hereditary illnesses like cystic fibrosis. The procedure involves introducing a small needle through the mother's belly into the amniotic sac to retrieve a fluid sample. This surgery has a less than 1% chance of miscarriage.Chorionic villus sampling (CVS)
According to Understanding Genetics, this operation is often performed between 10 and 13 weeks of pregnancy and includes inserting a small needle through the belly or a catheter through the cervix to obtain a small tissue sample from the placenta. The sample is then analysed for chromosomal disorders such as Down syndrome or particular genetic tests, with an accuracy rate of approximately 99 per cent; there is a 1 per cent possibility of miscarriage.Pros and Cons of Genetic Testing During Pregnancy
Prenatal genetic screening and diagnostic tests are optional at all stages. It's recommended that all expecting parents should be aware of their testing options during pregnancy. Genetic testing is optional and is never required. Because these tests are optional, you have complete discretion over whether or not to take them.Some pros and cons to consider are:
Pros:
- Results that indicate a minimal risk of genetic diseases can bring peace of mind.
- In the event of a diagnosis, parents have time to process the news before beginning to care for their newborn.
- Early diagnosis allows parents to learn how to support their child and create home accommodations for the baby's requirements.
Cons:
- Genetic screening tests estimate risk but do not diagnose.
- Genetic screening tests are not yet FDA-approved (Food And Drug Administration)
- Genetic diagnostic tests are more invasive, with a low chance of miscarriage.
Experts suggest that parents consider the following considerations while assessing the benefits and drawbacks of prenatal genetic testing:
- Is it beneficial to me to go through the screening process?
- Am I willing to undergo diagnostic tests?
- What information is vital to me? What information do I require?
- What should I do with this information?
If you want to proceed with genetic diagnostic tests, you will need to see a specialist. To find one, request a reference from your provider to identify a competent specialist in your area.
What To Do With Your Prenatal Genetic Testing Results?
According to the experts, findings from genetic screening tests are usually available within one week, and your doctor will most likely contact you with the results. Prenatal genetic diagnostic test results usually take about two weeks (depending on the test); your genetic counsellor will go over the results with you.If a genetic diagnostic test comes out abnormal, experts recommend that you consult with a genetic counsellor about the diagnosis, outlook, and next steps. Depending on the specific condition present and the family's expressed goals, options that may be presented include prenatal or postnatal treatment, delivery at a hospital with paediatric specialists, meeting with subspecialty care providers, adoption, abortion and palliative care.
Genetic testing during pregnancy may give useful information. However, when it comes to prenatal genetic testing, doctors should provide you with all of the information and support you need to make the best decision for your growing family.
FAQs on Pros and Cons of Genetic Testing During Pregnancy
- What week of pregnancy does genetic testing occur?
It depends on the test. Most providers conduct genetic testing after 10 weeks and before 22 weeks of pregnancy. Neither screening nor diagnostic testing are currently possible before 10 weeks gestation. - Are genetic screening tests harmful to your health?
No, they're not bad for you. Diagnostic tests such as amniocentesis and CVS (Chorionic villus sampling) carry some risk. That is why diagnostic tests are only performed when a genetic disease is suspected, rather than as part of routine prenatal genetic screening.
