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.

Transcript

00:00

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.

00:09

So we can see what the baby's chromosomes look like. [MUSIC PLAYING]

00:20

Well, existing screening is a combination of a blood test from mom, looking at chemicals in the mom's blood, PAPP-A and hCG,

00:29

combined with a specialized ultrasound of the fetus, called a nuchal translucency.

00:35

And then there's a second blood test that can be done later in pregnancy. Sometimes a woman does one or the other.

00:42

Sometimes we do both, and we combine the results and get a final result. That existing genetic screening is exactly that.

00:49

It doesn't identify a problem. It doesn't identify a genetic change. It gives us a risk.

00:56

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

01:07

essentially a no. If your baby has a risk of 1 in 50, then you probably want to do further testing

01:14

beyond the screening to get a diagnosis. So that's the second set of existing genetic testing

01:20

that we have. And those are what are called invasive tests. Chorionic villi sampling, where they, early in pregnancy,

01:27

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.

01:36

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.

01:42

We can see with the baby cells. Those test are 99.9% accurate with very low

01:49

false-positive rates. So they're the gold standard. New to the picture now is NIPT, Noninvasive Prenatal Testing--

01:56

blood tests on mom that looks for fragments of the fetal cells. And it is very accurate, ranging,

02:06

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

02:15

we'll find a trisomy 21 if it's there. [AUDIO LOGO]