Should I get prenatal genetic screening? The most common questions, answered. – Motherly Inc.

Posted: September 9, 2020 at 4:56 pm

Many people are surprised to learn how many decisions need to be made throughout pregnancy. Where do I want to receive my prenatal care? What lifestyle changes am I going to make to stay as healthy as possible?

Another big decision that needs to be made is about genetic screening during pregnancythere are so many options, and it can feel overwhelming. But take heart, mama. We promise you'll figure it out. Especially because you don't have to do it alone.

It's important to know that genetic screening is optional during pregnancy. Whatever feels right for you and your baby is usually best. New information on genetics comes out all the time. If you are thinking about having prenatal genetic screening or testing, talk to your provider first for the most up-to-date information and specific guidance based on your personal story.

According to the American College of Obstetricians and Gynecologists (ACOG), "prenatal genetic screening gives parents-to-be' information about whether their fetus has a certain genetic disorder."

Screenings are not diagnostic. This means that the results are not definitive ("The baby does or does not have Down syndrome,") but rather a prediction of chance ("There is a higher or lower than normal chance that the baby could have Down syndrome.")

If tests come back indicating that there is a high chance of abnormality, your provider may recommend diagnostic testing which can give a definitive yes or no result (more on that soon).

There are two main types of prenatal genetic testing: prenatal screening test and prenatal diagnostics test.

Prenatal screening tests:

Prenatal genetic screening tests can identify whether your baby is more or less likely to have certain birth defects, most stemming from genetic disorders. These are not definitive tests, they just tell you the chances. If results indicate an increased risk, your provider may talk to you about doing a diagnostic test.

Here are some common prenatal genetic screening tests:

Noninvasive prenatal testing (NIPT), also called cell-free fetal DNA testing. This can be done between weeks 10 and 20. It assesses the chances of chromosomal abnormalities, such as Down syndrome (trisomy 21), Patau syndrome (trisomy 13), Edwards syndrome (trisomy 18) and certain single-gene disorders associated with abnormalities of the skeleton, bones or heart. This test can also determine the sex of your baby if you'd like to know. The results take about a week to come in.

First-trimester combined screening. This is an optional test that is offered between weeks 11 and 14. The test involves taking a blood sample from you along with doing an ultrasound that looks at certain aspects of the baby's development. Specifically, the ultrasound looks at the clear space in the tissue at the back of the baby's neckthe size of this space, along with the information provided by the blood test, can help identify a higher chance for Down syndrome.

Second Trimester screening. Similar to the first trimester screening, your provider will take a blood test called a quad screen. This will measure four substances in your blood which indicate the chance of carrying a baby with chromosomal defects like Down syndrome, as well as neural tube defects.

Here are some common prenatal diagnostic tests:

Your provider may recommend a diagnostic test if your screening indicates an elevated chance of abnormality, or if other factors like family and medical history warrant it. These are more invasive and the only way to be sure of a diagnosis.

Chorionic Villus Sampling (CVS). CVS tests for certain disorders and chromosomal abnormalities in the fetus by looking at the chorionic villi, which are wisps of placental tissue that contain your baby's DNA. It can be done as early as 10 weeks. Placental tissue is extracted from your uterus by a catheter inserted into your cervix or by needle into the abdomen. The tissue will be genetically analyzed for certain disorders.

The procedure carries a small (0.35%) risk of miscarriage. It may sting and induce some cramping, but after a day of rest, you are cleared to resume normal activity. The benefit of CVS is that it can be done earlier in the pregnancy than an amniocentesis.

Amniocentesis. An amniocentesis (often called an amnio) is a procedure to sample the fluid that surrounds the baby. This amniotic fluid contains your baby's DNA, so it can be used to test for genetic disorders. It is usually performed between weeks 15 and 20 and does carry some risks, so it is important to be informed about them. According to the Society for Maternal-Fetal Medicine, amniocentesis is associated with a miscarriage rate of 1 in 300 to 500.

With most tests, there is a potential for false-positive results (when a positive test is wrong) and false-negative results (when a negative test is wrong). We recommend reaching out to your provider, they can give you more information on the rates of false-positive and false-negative test results and compare other options.

The risk associated with genetic testing can depend on the test you get. For the prenatal screening tests, the risks are limited due to its less invasive process (blood test and ultrasound). Many of the risks associated with genetic testing involve emotional, social and financial consequences of the test results. These are just as important to keep in mind (more on these in a bit).

For diagnostic screening, there is a small but real risk of miscarriage due to it being a more invasive procedure. This is because they need a sample of amniotic fluid or tissue from the fetus.

If you are trying to decide if you'd like to have genetic screening or testing, here are some questions to ask your provider:

There are also genetic specialists who may have even more information about the prenatal genetic testing than your provider does. Do not hesitate to request an appointment with a genetic specialist to discuss any of your questions further.

Mama, trust yourself. People are going to have all kinds of advice regarding genetic screeningsand it's okay to listen if you want to. But ultimately, you have to make the best decision for you. This is a great time to tune out the noise, get evidence-based and personalized information from your provider, and then listen to your gut. There is no right answer here, so doing what feels right is totally appropriate.

Some women choose to have all the available tests done, while others decline all of them. The majority of women probably fall somewhere in the middle.

Mama, it's all okay.

Here's a way to make the decision: Think about what you are going to do with the information you receive. Consider this:

If the test comes back saying your baby has a very low chance of having a chromosomal abnormality, will that help you to feel more relaxed during your pregnancy? Or would you rather not think about this knowledge one way or the other?

If the test comes back saying that your baby has a high chance of having a chromosomal abnormality, will you then choose to have an amniocentesis to get more reliable information?

If you do choose an amniocentesis, and it reveals that your baby does indeed have a chromosomal abnormality, does that impact your decision-making moving forward? Will you, for example, appreciate knowing this information so you can begin to make special plans for caring for the baby? Will you choose to terminate the pregnancy? If the answer to both of those questions is no, perhaps you may not want to have the testing at all.

Again, it's complicated. But just like with all of pregnancy and parenting, there is no one right way to do things. The world is full of ideas and judgment, but in these moments, focus on your needs and desires and your provider's guidance.

A portion of this article has been excerpted from The Motherly Guide to Becoming Mama.

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