Prenatal Genetic Testing: What You Need To Know

Nobody likes tests. They are by far the biggest cause of sudden nausea, cold sweats, anxiety and tears in school. It’s much the same for prenatal genetic testing. Except there’s less opportunity to get out of it by faking a fever and whining to your mommy.

Prenatal genetic tests help parents understand the likelihood that their child could be born with any number of genetic disorders that range from open neural tube defects to Down syndrome. While your doctor will be more than happy to explain the options (and bill you), here’s an overview so you can go in prepared to act:


Types of Prenatal Genetic Testing
“Testing” is essentially a global term for all the various ways your partner can be poked, prodded or scanned. The two subcategories to testing are screening and diagnostic tests (and not nerve-wracking and more nerve-wracking, as you might have thought).

flickr / Joshua Yoon Hernandez

flickr / Joshua Yoon Hernandez

Screening: These tests are usually the first to be done. They will use the mother’s blood serum and a specialized ultrasound to determine the risks of certain genetic issues. They also come with a tremendous caveat: the results of screening can only tell if there is an increased risk. It does not mean your child is necessarily afflicted by a genetic disorder even with higher risk indications.

Diagnostic Testing: When it is determined that there is an increased risk for genetic issues, diagnostic testing will be recommended. These tests come second because they are invasive and rely on amniotic fluid and placental samples. Because of that they also carry a small risk of complications that include miscarriage.

Screening Tests
Nuchal Translucency: This sounds like something more likely associated with a deep-sea jellyfish. But the nuchal translucency screening is a specialized ultrasound that measures the thickness of your kids neck, which determines if they could be affected by issues like Down syndrome (or just getting hella jacked with in-utero free weights). It’s performed in the first trimester by someone who is specialized in the procedure.

flickr / Zach Chisholm

flickr / Zach Chisholm

Blood Tests: Using the mother’s blood (thank goodness, right?), this screening looks for a variety of protein and hormonal markers that are associated with an increased risk of anencephaly, spina bifida and Down syndrome. These are also performed in the first trimester.

Diagnostic Tests
Amniocentesis: Brace yourself for this one.  Through the abdomen and into the womb, a fine needle is inserted. Then, a tiny amount of amniotic fluid containing live fetal cells is extracted  Live fetal cells from a tiny amount of amniotic fluid. If you aren’t squeamish about needles (you freak) then go ahead and be there for this one.

This test is the most accurate way to determine a large number of genetic abnormalities. And as a consolation prize, is also the most accurate way to determine the kid’s sex. Because it is invasive, it does carry with it some small risks to both the mother and the baby. It can be done up to the third trimester of pregnancy in some instances.

flickr / Alden Chadwick

flickr / Alden Chadwick

Chorionic Villus Sampling (CVS): Try not to confuse this one with where you get your prophylactics and Steel Reserve. This test samples tissue from the placenta via a small tube inserted through the cervix. It can be done as early as week 10. Unlike amniocentesis, CVS doesn’t detect neural tube defects. It also comes with a slightly more elevated risk for complications.

Is Testing Always Required?
Screening and diagnostic testing is not compulsory and there are plenty of reasons a couple may not want to go down the testing road. One of the biggies is that these tests can sometimes result in false positives that could lead to further unnecessary testing and add a ton of undue stress.

There’s also the anxiety factor. Some feel that knowing their child has a genetic disorder would not change how they would approach the remainder of the pregnancy. Therefore they may opt out of testing to avoid that kind of anxiety.

flickr / Pascal

flickr / Pascal

However, your doctor will encourage prenatal tests in a few specific instances:

  • The mother is over the age of 35, which is considered an advanced age for pregnancy and makes you feel like you’re in Logan’s Run
  • You have a previous child with a chromosomal disorder
  • There is a disorder that runs in your family (aside from being annoying at Thanksgiving)
  • You and your partners both carry a recessive gene linked to a birth defect

You can keep calm by going in informed, despite the fact thats tests are universally reviled and stress inducing. And at least with prenatal testing there aren’t any Scantrons. So no need for a perfectly sharpened number 2 pencil. Bonus!


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