What is genetic testing?
Prenatal genetic testing evaluates your fetus’ risk for different genetic conditions. Genetic conditions are disorders that are coded for in your DNA. Sometimes a fetus may have missing or extra chromosomes, and other times it may have an inherited condition. Although you may not have a condition yourself, you or your partner may be a “carrier” for an abnormal gene. If you are a carrier for an abnormal gene, your baby may be at risk of inheriting that specific disorder1.
What kinds of things do you look for in a genetic test?
Genetic testing can test for an inherited condition for which you or your partner may be a carrier. These disorders include, but are not limited to:
- Cystic fibrosis
- Fragile X syndrome
- Tay-Sachs disease
- Spinal muscular atrophy
Genetic testing can also screen for abnormalities in chromosome numbers. Conditions in which an individual has a missing or extra chromosomes include:
- Down syndrome
- Edwards syndrome
- Patau syndrome
- Turner syndrome
- Klinefelter syndrome2
Who is at risk of having a child with a genetic condition?
Genetic disorders and birth defects are not common, but certain racial and ethnic groups are at increased risk of certain conditions. These groups and associated disorders are summarized in the table below.
| Racial / ethnic group | Genetic condition |
| Ashkenazi Jewish descent | Tay-Sachs, cystic fibrosis |
| Mediterranean descent | Thalassemia, sickle cell disease |
| European Caucasian descent | Cystic fibrosis |
| Southeast Asian descent | Thalassemia |
| African American | Thalassemia, sickle cell |
| French Canadian | Tay-Sachs, cystic fibrosis3 |
What types of genetic testing are there?
It is important to understand the difference between a screening and diagnostic test. A screening test lets you know the chances of your baby having a genetic abnormality. A diagnostic test confirms whether the fetus actually has a genetic abnormality1.
A diagnostic test should always follow a positive screening test. A diagnostic test can confirm whether the fetus has a condition. Therefore, you should not make an irreversible decision based on just a screening test2.
How is genetic testing performed?
The method of testing will depend on the type of test you undergo. Different methods and what the methods screen for are outlined in the table below.
| Method | Genetic condition screened for |
| Cell-free DNA testing | Down syndrome, Edwards syndrome (trisomy 18), Patau syndrome (trisomy 13), issues with multiple chromosomes |
| Ultrasound | Physical defects, Down syndrome, other aneuploidies (missing / extra chromosomes) |
| Blood tests | Down syndrome, Edwards syndrome1 |
Who should get genetic testing?
Anyone who is pregnant can receive prenatal testing. Commonly, pregnant woman over age 35 decide to undergo screening. This is because the risk of having a child with a chromosomal abnormality increases with increased age. However, there are many other reasons a woman may decide to undergo testing. These include, but are not limited to:
- Abnormal findings on an ultrasound
- A family history of a certain genetic condition
- A previous child with a specific genetic condition
- Positive screening test results
If you have concerns about genetic conditions, talk to your obstetrician or genetic counselor about what testing options are available and right for you4. Undergoing screening early can help you make decisions about your pregnancy, prepare for your baby, and potentially help your child have a healthier life3.
References
- Prenatal genetic screening tests. (n.d.). Retrieved January 8, 2022.
- Gordon, S., & Langaker, M. D. (2021). Prenatal genetic screening. In StatPearls. StatPearls Publishing.
- Genetic testing during pregnancy: What you need to know – Insider. (n.d.). Retrieved January 8, 2022
- Alliance, G., & Screening Services, T. N. Y.-M.-A. C. for G. and N. (2009). Prenatal screening and testing. Genetic Alliance.