How does non-invasive prenatal testing compare to existing screening and testing?
Non-invasive prenatal testing (NIPT) screens a mother’s blood, while the existing invasive testing screens samples of chorionic villi and amniocentesis. In this video, Patricia Geraghty, NP, further compares both types of prenatal testing.
Chorionic villi sampling, where they, early in pregnancy, take a sample of what will become the placenta, that has baby cells in it, fetal cells in it.
So we can see what the baby's chromosomes look like. [MUSIC PLAYING]
Well, existing screening is a combination of a blood test from mom, looking at chemicals in the mom's blood, PAPP-A and hCG,
combined with a specialized ultrasound of the fetus, called a nuchal translucency.
And then there's a second blood test that can be done later in pregnancy. Sometimes a woman does one or the other.
Sometimes we do both, and we combine the results and get a final result. That existing genetic screening is exactly that.
It doesn't identify a problem. It doesn't identify a genetic change. It gives us a risk.
So the results are reported as a risk of one in. Now, if your baby has a risk of 1 in 2,000 of having, for example, three 21 chromosomes, that's
essentially a no. If your baby has a risk of 1 in 50, then you probably want to do further testing
beyond the screening to get a diagnosis. So that's the second set of existing genetic testing
that we have. And those are what are called invasive tests. Chorionic villi sampling, where they, early in pregnancy,
take a sample of what will become the placenta, that has baby cells in it, fetal cells in it. So we can see what the baby's chromosomes look like.
Or a little bit later in the pregnancy, where they take a sample of the amniotic fluid, which again, has free-floating baby cells in it.
We can see with the baby cells. Those test are 99.9% accurate with very low
false-positive rates. So they're the gold standard. New to the picture now is NIPT, Noninvasive Prenatal Testing--
blood tests on mom that looks for fragments of the fetal cells. And it is very accurate, ranging,
depending upon which chromosome they're looking at, from about 83% of the time we'll find something that's there, up to 99% of the time
we'll find a trisomy 21 if it's there. [AUDIO LOGO]
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