Pregnancy

NIPT – To Screen or Not to Screen

NIPT tests are screening tests for trisomies that are offered to women over 35. They have proven to be correct more often, meaning predicted the correct outcome, more often than the previous first trimester screening. They take just a simple blood sample and can be performed as early as 10 weeks. Common names are MaterniT21, Harmony, and Natera.

During my pregnancy with my oldest son, I was offered the Harmony NIPT test. My doctor was out of the test kit so I left with a lab requisition and was to come back in a few days.  On my way home I started thinking that I recalled seeing something on the news about these tests, but couldn’t put my finger on it. 


Once home and researching, I found the segment I had seen.  The story is here:https://www.nbcnews.com/health/womens-health/prenatal-tests-have-high-failure-rate-triggering-abortions-n267301

Basically it was a false positive for Edwards syndrome and a false negative for Downs syndrome.  This lead me down a rabbit hole of research and ultimately to understand the limitations of the tests better. 


Here is another example of a sad false negative and false positive. https://www.wgbh.org/news/2014/12/13/oversold-and-misunderstood

So next I went looking for my real risk. It’s true that at 39, my risk of having a baby with downs syndrome was 18 times higher than when I was 25, but what does that really mean?  The truth is that at 39 years old, I had a 0.73% chance of having a baby with downs and 1.2% of having a baby with any trisomies.  So I had a 98.8% chance of having a normal baby, based on my age and stats alone. 

 You can check your risk level here:https://embryology.med.unsw.edu.au/embryology/index.php/Genetic_risk_maternal_age

I then found this link which tells me the chances that a positive per each issue is a true positive or false positive.  It was pretty shocking to me, as some combos come up to 50/50.  I could flip a coin.  https://www.perinatalquality.org/Vendors/NSGC/NIPT/

So ultimately I concluded that I would be screening to see if my baby fell into the tiny statistic and then if I actually got a positive, I would either assume a small risk of miscarriage to confirm or disprove the result, or spend the rest of my pregnancy worried.  
Combine all of that with our perfect NT scan and it just didn’t seem worth it to me.  Kind of a waste of effort (like these whole grain cheez it’s Delta is now giving out on flights!?)

Most of the time the tests results are right.  Much of the time it is valuable and puts people at ease. I have seen a ton of women take them and they are correct and all is fine with their baby and they enjoyed knowing the gender early.  I have seen one woman get a positive for Patau, do a confirmatory amnio and lose her normal baby to infection after.  Maybe it wasn’t the amnio, she will never know, but she regrets her decision so much.   I have seen women refuse the amnio and have stressful pregnancies, some resulting in normal babies, and some not.  Often the ones that do not also have obvious markers on ultrasound.  

On the flip side, I have seen the test identify a rare disorder, XXY, Klinefelter syndrome. This is often not found and if known, treatment can be given early that can make a marked difference in that boys life. In these cases, those tests are blessings, making the decision to test or not even more complicated.

To NIPT or not is really a very personal decision that should be made by the couple. If you have any doubt or questions, you should have access to a genetics counselor. Just be sure if you see one you are clear on who signs their paycheck, as some work for the testing companies. A non-biased third party can help you choose.

I would love to hear opinions on these tests.