Your prenatal appointments are considered an essential foundation of your health, and your baby’s, as you make your way through a nine-month journey together. In addition to strengthening your bond with your OB, midwives, and labor/delivery team, these appointments offer the ability to test for some of the most common genetic disorders or abnormalities that affect a baby’s well being.
It’s important to note that the results of genetic screening tests are not 100% accurate. However, over the duration of your pregnancy and with more genetic testing, we can achieve more accurate results.
What are Genetic Disorders?
Any abnormal changes in a person’s chromosomes or genes lead to a genetic disorder. Examples include:
- Aneuploidy. Having missing or extra chromosomes is called aneuploidy. Examples of aneuploidy include Down’s Syndrome (extra) and Turner’s Syndrome (missing).
- Inherited factors. If a certain genetic disorder runs in the family, or is more common to a particular race, parents can pass that genetic disorder onto their children. Examples of these include Tay Sachs disease, cystic fibrosis, and sickle cell disease.
- Environmental or unknown causes. Sometimes, babies are born with genetic disorders and we just don’t know why. Environmental toxins can be a culprit as can medication or lifestyle choices or poor egg or sperm quality (one of the main reasons age plays such an important role in fertility).
We can use prenatal genetic screening tests to help determine whether or not a fetus or baby has a chromosomal or genetic disorder. These tests are broken into a few categories:
- Preconception genetic testing
- First-trimester screening
- Second-trimester screening
- Combined first/second-trimester screening
- Cell-free DNA testing
Knowing the results of these tests ahead of time helps parents and healthcare providers to make more informed decisions about pregnancy, labor, and delivery plans.
All of these tests are 100% voluntary, and your pregnancy care provider will help you determine which if any (or all) make the most sense for you based on your appointment conversations.
Preconception Genetic Screening
Parents can begin the genetic screening process before they ever conceive a child by having their own genes tested. We call this preconception genetic screening. It consists of a simple blood and/or cheek tissue sample test that screens for the most common genetic disorders. Costs for these tests are usually totally or partially covered by insurance.
We start by testing the mother. If she is a carrier for a particular genetic disorder, we’ll test the father as well. From there, you can discuss your fertility options.
The most common prenatal genetic screening tests offered during the first-trimester, usually between weeks 10 and 13, include:
- Ultrasound. Throughout your pregnancy, you’ll be offered monitoring tests, one of the most common being ultrasound imaging. In addition to the absolute joy of seeing your baby in utero, these imaging tests also allow us to see if the baby is progressing along a normal, developmental timeline, with all parts in the correct numbers and places. If we notice anything abnormal, we’ll recommend further testing or diagnostic procedures.
- Nuchal translucency screening. During your ultrasound, we’ll measure the thickness in the space at the back of the fetus’s neck. An abnormal measurement here could mean the baby has aneuploidy such as Down’s Syndrome. Conditions like these can also affect other parts of the baby’s development, such as his/her heart, skeleton, or abdominal wall.
Second-Trimester Genetic Screening
During the second semester, we’ll offer an expanded screening test menu.
- Quadruple (quad) blood tests. You’ve given blood already, but those samples were more about your overall blood counts rather than genetic information. Second-trimester blood tests are referred to as “quad” blood tests because they screen for four different substances in your blood. The presence of these substances can indicate genetic disorders such as Down’s Syndrome, Edward’s syndrome (trisomy 18), or neural tube defects.
- Ultrasound. This time around, we’ll be looking to see if there are any obvious signs of physical defects, such as defects of the limbs, facial features, brain/spine, abdomen, and the heart. Some of these can even be treated in-utero, or immediately after delivery, which is why it’s so important to know about them as soon as possible.
Individually, these tests are not always 100% accurate or conclusive. Therefore, we used combined first- and second-trimester test results to create more conclusive and trust-worthy results.
Cell-free DNA testing
Once your fertilized egg implants into the uterus and begins developing, small amounts of DNA from the fetus is released through the placenta and into the mother’s blood stream. This allows us to “read” the fetus’s DNA through cell-free DNA testing.
A “positive” cell-free DNA test result means a genetic disorder has been detected. But again, remember that these tests aren’t always accurate. Your healthcare provider will recommend further testing, via amniocentesis and/or Chorionic villus sampling (CVS) to get more information.
Are you overdue for your first or second-trimester prenatal appointment or genetic screening tests? Schedule an appointment with us here at Overlake OB/GYN.