Pregnancy is an exciting yet critical time in a woman’s life. Expecting parents often find themselves overwhelmed with decisions to ensure the health and well-being of their baby. Among these decisions is whether to undergo genetic testing or not. With advancements in prenatal testing, two major genetic tests have become widely discussed: Carrier Screening and Non-Invasive Prenatal Testing (NIPT). Both tests offer valuable insights into the health of the baby, but each serves a unique purpose. 1
Understanding Genetic Testing During Pregnancy
Genetic testing during pregnancy helps detect potential genetic disorders in the fetus or identify whether the mother or father is the carrier of genetic conditions that could be passed to their child. Prenatal genetic testing can help in making informed decisions about the pregnancy and the health of the baby. There are several types of genetic tests available, including carrier screening and NIPT. The choice of test depends on factors such as family history, ethnicity, and personal preferences. 1 2
What is Carrier Screening?
Carrier screening is a genetic test that is performed before or during pregnancy to determine whether one or both parents carry a gene for a recessive inherited condition. Some genetic conditions are caused by mutations in a single gene, and if both parents are carriers, there is a 25% chance that their child will inherit two copies of the mutated gene (one from each parent) and develop the condition. Common conditions tested in carrier screening include sickle cell anemia, cystic fibrosis, and Tay-Sachs disease, to name a few. 3
Carrier screening is often recommended for couples with a family history of genetic disorders or those belonging to ethnic groups with a higher risk of certain genetic conditions. The test is performed with a simple blood sample or cheek swab and can be done at any time before or during pregnancy. 3
What is NIPT Testing?
Non-Invasive Prenatal Testing (NIPT) is a blood test that analyses small fragments of fetal DNA (cfDNA) circulating in the mother’s blood. It screens for specific chromosomal conditions in the fetus, such as Down syndrome (trisomy 21), trisomy 18, and trisomy 13. NIPT is non-invasive, which means it carries no risk of miscarriage, unlike invasive tests such as amniocentesis or CVS. 2 4 5
NIPT is a highly accurate screening test that can be done as early as the 10th week of pregnancy. While NIPT provides valuable information about chromosomal abnormalities, it does not currently test for other types of genetic disorders, such as those screened for by carrier screening. The main advantage of NIPT is its ability to detect conditions that affect the chromosomes early in pregnancy with a high degree of accuracy. 6
Carrier Screening vs NIPT – Key Differences
| Feature | Carrier Screening | NIPT (Non-Invasive Prenatal Testing) |
| What it tests for | Inherited genetic conditions (e.g., cystic fibrosis, sickle cell) | Chromosomal abnormalities (e.g., Down syndrome, Trisomy 18) |
| When it’s done | Before or early in pregnancy, or preconception | After 10 weeks of pregnancy |
| How it’s done | Blood or buccal swab for both parents | Blood test from the mother |
| Purpose | Identifies if parents are carriers for recessive genetic disorders and X-linked disorders | Identifies the risk of the fetus having chromosomal conditions |
| Risk Assessment | Identifies carrier status for both parents | Estimates the risk of chromosomal abnormalities in the fetus |
| Diagnostic or Screening? | Screening test for carrier status | Screening test for fetal chromosomal abnormalities 4 7 8 |
Can You Do Both Carrier Screening and NIPT?
Yes, you can do both carrier screening and NIPT. In fact, many couples choose to undergo both tests to get a comprehensive understanding of their genetic risks.
- Carrier screening provides information about inherited genetic disorders, especially if both parents are carriers of a recessive gene.
- NIPT test helps detect potential chromosomal abnormalities in the fetus.
These tests complement each other, providing a more complete picture of both the parents’ genetic makeup and the fetus’s health. In some cases, if a carrier screening reveals that one or both parents are carriers of a genetic disorder, NIPT can be used to evaluate whether the fetus has any chromosomal abnormalities. 2
Genetic Counseling in Prenatal Testing:
Whether you opt for carrier screening or NIPT, genetic counseling is an essential part of the prenatal testing process. A genetic counselor can help comprehend the results of these tests, explain their implications, and provide support in making informed decisions. Genetic counseling can also help you understand your options if a test comes back positive for a genetic condition, such as further diagnostic testing or exploring options for managing the pregnancy.
Genetic counseling is particularly important if you have a family history of genetic disorders or if you belong to an ethnic group with a higher prevalence of certain inherited conditions. A counselor can also help explain the emotional and psychological aspects of the testing process and support you in making the best decisions for you and your family. 8 9
Conclusion
Choosing between carrier screening and NIPT depends on the specific information you wish to learn during pregnancy. Carrier screening is an excellent option for identifying inherited genetic conditions that may be passed down from one or both parents. NIPT, on the other hand, provides crucial information about chromosomal conditions that could affect the fetus.
MedGenome is a leading provider of genetic testing services, offering both Carrier Screening and NIPT, among other advanced genetic tests. MedGenome combines cutting-edge technology with genomics expertise to provide precise, comprehensive genetic testing services that enable individuals and healthcare providers to make educated pregnancy decisions.
References
1 Prenatal Genetic Testing Chart. (n.d.). ACOG. https://www.acog.org/womens-health/infographics/prenatal-genetic-testing-chart
2 Genetic Carrier Screening vs NIPT | Monash Ultrasound for Women. (2024, January 18). Monash Ultrasound for Women. https://monashultrasound.com.au/services/prenatal-testing/screening-options/
3 Professional, C. C. M. (2024b, September 9). Carrier Screening. Cleveland Clinic. https://my.clevelandclinic.org/health/diagnostics/carrier-screening
4 Shiraz, Z. (2024, May 30). Non-invasive prenatal testing: Purpose, advantages, risks and limitations of NIPT. Hindustan Times. https://www.hindustantimes.com/lifestyle/health/noninvasive-prenatal-testing-purpose-advantages-risks-and-limitations-of-nipt-101717075156660.html
5 What is noninvasive prenatal testing (NIPT), and what disorders can it screen for?: MedlinePlus Genetics. (n.d.). https://medlineplus.gov/genetics/understanding/testing/nipt/
6 Professional, C. C. M. (2024b, May 1). NIPT Test. Cleveland Clinic. https://my.clevelandclinic.org/health/diagnostics/21050-nipt-test
7 Royal College of Pathologists of Australasia. (2014). Non-invasive prenatal testing. Royal College of Pathologists of Australasia. Retrieved from https://www.rcpa.edu.au/Library/Publications/Common-Sense-Pathology/Docs/2014/Non-invasive-Prenatal-Testing
8 Gordon, S., Umandap, C., & Langaker, M. D. (2023, January 16). Prenatal Genetic Screening. StatPearls – NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/sites/books/NBK557702/
9 Alliance, G. (2008). Prenatal genetic counseling. Making Sense of Your Genes – NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK115507/
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