Genetic Screening Blood Tests - PLEASE READ
Sorry in advance for the length. I often sit on my hands when I read some things on this forum, but I can't on this issue. Please, please read to the end, especially if you've had genetic screening blood draws or intend to in the coming weeks..
I've seen a lot of excitement about the non-invasive prenatal tests now offered via blood draw. These tests are wonderful tools to learn your baby's sex before the traditional 15-20 week ultrasound window. They also offer the ability to better understand your baby's risk for genetic abnormalities without having to undergo a riskier/more invasive amnio or CVS. However, I've encountered a lot of women advising others that these tests are 99% accurate in diagnosing abnormalities. Having a background in genetics, I am super troubled by this rampant misinformation. These are screening tests, not diagnostic tests. MaterniT21, Harmony, Progenity and the others are all unregulated lab offerings that claim to be able to provide yes or no results. I'm pretty sure one lab uses the slogan "Yes or No, never Maybe"... That's just NOT true. These tests are able to confirm with 98-99% accuracy a positive predictive value. For example, it can confirm that your risk for having a child with the chromosomal abnormality that causes Down syndrome is 1 in 4. That doesn't mean your unborn child has Down syndrome. It means that there is a 1 in 4 chance. The ONLY way to know for certain is to proceed with an amnio or CVS.
I definitely think there's utility in these tests (heck, I'm waiting for my own results), but I encounter many patients and even physicians who do not understand these offerings and misinterpret results. The outcome of misinterpreted results can be devastating, in some cases leading women to terminate what would have been healthy pregnancies. I don't want to scare anyone -- quite the opposite. I want to ensure that women who have positive screens understand what that means for their families and that they ask for all appropriate follow up screens and testing before making any decisions. Certainly some women will carry a child to term no matter the news, but others may seek alternative paths when the need to isn't present. I want to encourage all of you to be thorough in completing your research for your own sake, but especially before you tell other women things that are patently untrue. I am happy to answer any questions, so please don't hesitate to ask. I wish everyone happy, healthy, well-informed pregnancies. If you have an interest in learning more about cell free DNA testing check out the following: