Originally Posted by alittlesandy
I want to chime in on the differences between the tests. Nuchal Translucency screening is a non-invasive ultrasound that is actually very accurate. However, I will NOT be having CVS or Amnio because of the risks.
I am a midwife, and agree that NT is more accurate than blood testing alone, but what it is particularly good at is RULING OUT conditions, not diagnosing them. If I were doing prenatal screening because I wanted access to this information, and my result came back positive/above the cut-off for a particular condition I myself certainly would want to confirm that with a diagnostic test, ie amnio. Especially if I were going to change my care provider or place of birth based on the screening result.
This is why:
The NT or NT+blood test result is still a risk estimate, ie 1:20 000, or 1:2000 or 1:200 or 1:20, and while the reassuring/low-risk/below screen cut-off/negative (however it's worded in your area!) results like the 1:20 000 or 1:2000 are quite reliable (ie. very few babies with the target condition are missed) the screening parameters are structured in such a way that many more women are identified as higher-risk/above the cut-off/positive than actually have babies with target condition. It's done this way on purpose so that very few people are missed. Some people call this a 'high false positive rate'.
So if my result were positive, there's still a good chance that the baby does not have the target condition, and I'd want to know for sure before I made any big decisions about how to manage the pregnancy, whether it be termination or different care provider or different place of birth.
Check out this visual aid that I find super helpful in explaining this to my clients.
I'm not doing prenatal screening by the way, but spend a lot of time helping clients figure out if they want to do it.
Edited by lalazap - 9/30/11 at 12:17pm