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Screening and Testing Strategies



So here we go. Strategy one is saying, “I’m not going to plan to do any of these things. You’ve made me nervous about this false positive stuff. Right? What if I see a little echogenic focus or something and get a phone call?” Now let me ask you this. Does it make you a bad mom if you’re not going to have a routine ultrasound? Does that mean you’re not being compliant … that you’re not doing something to help the baby? It doesn’t. It doesn’t because the studies say that doing an ultrasound does not change the outcome, if you just do it on everybody. Now could you say, “I’m not planning on a screening test Dr. Fausett,” but still end up with an ultrasound? You could, because let’s say you’re going along and we’re measuring your tummy and all of a sudden we find out that you’re measuring a lot bigger than you’re supposed to. Now you have an indication for an ultrasound.

Now we go do the ultrasound for the indication, okay. So that helps us to know … oh yeah, okay. And, in fact, what if we did that and we saw that you were measuring really big because there was a ton of amniotic fluid and it’s because something was wrong with the baby, and we found that on ultrasound. Then you could even have an amniocentesis. Right? So, just because you’re not planning on screening, doesn’t mean you couldn’t end up with a diagnostic test. It just means you’re not going looking necessarily for that in that screening test. Does that make sense? Yes. So I’m not trying to talk you out of doing an ultrasound. Most people want one. Okay. But what I am trying to help you understand is there’s a little bit of risk, you know, by finding things that might make you nervous and what are you going to do about it. Okay. All right. So, that’s the first one. And, of course, that would also mean if you’re not doing any tests, you’re not doing any of those blood tests. All right.

So what are the possible benefits of not doing any screening? Well, maybe you want to avoid all those false positive findings, potential findings, and maybe you want a surprise. It seems like we’re not very patient these days. Most people want to know. Like, “Tell me.” I just found out I’m pregnant. Is it a boy, you know and they’re asking me to tell them and I can’t tell yet. Right. They look the same right now. All right, but some people might want that surprise.

So what are the downsides of just doing that — of saying, “I’m not going to do any screening tests?” Well, although it doesn’t really help us change the outcome, remember you said one of the benefits of looking early is preparing. And so you might not know something was coming and that might be more of a challenge for you. So that’s maybe one of the downsides of not doing screening. And the ultrasound does help us to confirm your dates. So if you haven’t had any ultrasound at all, it does help us to some degree. Now if you have a regular menstrual cycle, we’re pretty good at estimating dates but ultrasound might help us. And that might affect things like future screening tests and other things that you might do. Okay. All right.

Strategy two this says, “I want that screening ultrasound. I’d like that 18-week to 20-week exam, and what can we get from that? What are the big benefits?” Well, we’ll confirm your dates, like I just mentioned, and we’ll screen for major structural problems. So if the baby had a big issue, we’d probably see it on ultrasound and that would help you to know about it. To be able to prepare for what was happening, or to try to understand what was happening. Okay. And obviously if you look with that ultrasound and everything looks good, that’s going to give you, hopefully, some of that peace of mind that we talked about in the beginning, and help you find some reassurance and feel better about things. And that can be a biggie, right? That reassurance.

So what are the downsides of doing that screening ultrasound? Well if we chose that for our strategy, it’s not quite as good as detecting Down syndrome as some of the blood tests. Remember that. But yet if you’re really mainly after structure and how do things look, then it’s a perfectly good test but it’s not as good at detecting Down syndrome as the blood tests. All right.

So who would want strategy two? Parents who want an ultrasound want to see. Somebody who says, “I’m really not after the aneuploidy screening thing. I just really want to make sure that things look normal. I definitely wouldn’t end a pregnancy if the baby had chromosome problems so I’m really after how does the baby look.” Then maybe that ultrasound is all you need.

All right. So, strategy three. So in this strategy we start with a second trimester quad screen, and this can be done again as early as 15 weeks and it has to be done before 22 weeks. Okay, so 15 to 22. We start with the quad screen or the second trimester blood screen, draw your blood and then you come up with a number. Okay. Now in our system typically if you come up with a number and you’re low risk, then you go to the radiologist and have a basic screening ultrasound to follow, if you’re going to have an ultrasound to follow. If you do the quad screen and it comes up high risk, then you usually get the consult and the referral to the maternal fetal medicine doctor or geneticist who does ultrasound. And then we have a look at the baby in more detail, and counsel you about the findings and offer you testing. Okay. So depending on what you find, you get the different kind of a follow on ultrasound. Okay. So that’s the biggie.

What the big benefit of doing strategy three? Well, we’re going to look with ultrasound and we’re going to draw blood, so those two tests are in combination very good at screening for chromosome problems and major structural problems. So, of course, if all that’s reassuring, it’s a nice dose of peace of mind right? It should help you give you a lot of peace of mind and give you some reassurance.

Now what’s the down side of doing both the ultrasound and the quad screen? Well, unfortunately the false positive rate of the ultrasound adds to the false positive rate of the quad screen, and you have higher risk of having a false positive test if you do both of those tests. So, in some sense, doing the quad screen plus the ultrasound has a higher chance of causing you worry, if you wouldn’t do anything about the testing. Does that make sense? If you would, then combining those two things together is a good way of screening because it’s pretty comprehensive. Okay.

So who would want this test? Again, probably parents who would consider using the results of the test to help them make a decision about continuing or not, and probably it would be people who would be willing to have an amnio. Okay. But not necessarily, but probably would be willing to or else you’re stuck in that … potentially get stuck in that situation. Now hopefully and again most people would get reassurance by that … by the two tests together. All right.

So, strategy four. We’re getting there, right? So this strategy we start with that first trimester screen. And we draw blood, look at the baby with ultrasound, and measure a clear space on the back of the baby’s neck called a nuchal translucency. And we put these two things together and come up with a risk. Okay. Now if this is done at 11–12 weeks, let’s say, and if we found out that a mom was high risk, what would we do? Well, then you could offer her an earlier diagnostic test, which is the CVS. Do you remember that? Yes. And so the biggest benefit of screening early, besides the fact that it has a good detection rate, is really that early result that can give you some privacy. For example, a lot of people may not know you’re pregnant that early, and if you want to know soon, if pregnancy termination is something you would think about, then the sooner you know about that, the better. Okay. So it doesn’t mean that you have to have a pregnancy termination if you’re going to do a first trimester screen, but if you’re going at it more aggressively, it tends to be because you would make a different decision. Okay.

So any down sides to doing the first trimester screening? Well, one potential down side is if you do the screening test and you find out you’re high risk, then the diagnostic test is the CVS. And for some people, the potentially slightly higher risk of a loss by doing a CVS is not acceptable and so some would say, “Oh, maybe I’ll have a diagnostic test, but I’m going to wait until the second trimester anyway.” And so if you draw your blood, find out you’re at high risk in the first trimester, but you’re not willing to have a CVS, then you’re going to be waiting at least until the second trimester to think about an amnio. Or you’ll go the rest of your pregnancy just knowing that you’re higher risk, looking with ultrasound and things like that. Now again, you don’t have to have CVS, but it makes most sense to do earlier screening if you’re to do earlier testing.

Okay. Any questions about that strategy? I have a question. Yeah. How do you do this, I guess, strategy if it was multiple babies? Ah, great questions. Twins or more. Great questions. Some of these strategies work, in fact all of them to some degree work, in multiples. For example, that first trimester screen — what you do is you take the average of the blood test because that’s a combination of both babies, right? But you also then take the individual nuchal translucency measurements, and so you can come up with an individualized risk per baby with the first trimester screen. You can’t really do that with a quad screen cause it’s just blood, but the ultrasounds themselves, the second trimester ultrasound also, you’re looking specifically baby per baby, and looking at them to see if they have risks for chromosome problems or other structural problems. So, they’re helpful. Now, there’s not as much data with multiples and so the tests aren’t as tight. Does that make sense? They’re not quite as accurate, you might say, but the idea works. Good. Any other questions about that one? All right.

So, now we’ll talk about diagnostic tests. We’ve gone through screening and you guys already know about the diagnostic tests so the question is, “Do I have to know for sure, and therefore am I willing to just go right for the amnio?” Because that can tell you yes or no. Right? About chromosome problems. All right. So if you say, “Well, I’d like to know for sure.” That’s a common definitive test, an amniocentesis, and we’ve talked about that a lot. Obviously, its down side is there’s some risk of miscarriage and it gives you a little bit later result than a CVS. All right. So who wants strategy five? Somebody who wants to know yes or no, willing to take the risk. Okay. All right.

Now, last one. This is probably the most aggressive strategy and that’s to go right for CVS in the first trimester. And it’s early, it’s diagnostic, it’s yes or no. And it allows you privacy, so that’s a good thing. The downside is, in most situations we have to refer you to somebody who does that all the time, because we don’t do CVS. And it’s probably a riskier test than the amniocentesis. So, a little bit higher risk of miscarriage. And then, as I mentioned, CVS … you can’t always get it, even when you try, and so although it’s usually diagnostic sometimes we’re unsuccessful at getting the test. Okay. So who wants strategy six? Moms who want to know as early as possible and need to know yes or no. Okay.

So typically if you want to go directly to a diagnostic test we’d sit down and talk to you a bit more and make sure that you wouldn’t want to do a screening test first, because if the screening test came back and said you were very low risk, maybe that would be reassuring enough for you. Okay. Because that’s the best biggest benefit of all the screening tests…finding out that you’re low risk. Yeah.

All right any questions about any of the strategies? I do have one question about the CVS in particular. Oh yeah. You said, it’s more dangerous than an amnio. Is the risk because, as you said, it’s done less frequently so it’s operator error? Is there something about the early part of the pregnancy that makes it riskier? Great question. It mostly has to do with just plain experience. They’re little nuances of how you move those catheters to sneak into that little space that relate to the risk. And, while generally, if you take everybody there’s a little higher risk of loss with CVS. People who do it all the time, who do lots and lots, their loss rate is at or lower than the average rate for an amniocentesis, so it really is very much provider dependent. Yeah. There is a little higher rate of miscarriage early, but that may be just natural because there’s a higher rate earlier. Sure. Okay does that make sense? Uh-huh, thank you. Good. Any other questions?

Dr. Fausett, I have a question. Sure, Jenny. With the amniocentesis, can you have it say in the third trimester, versus the first or the second? Yes. You can have an amnio all the way up until there’s no more amniotic fluid, and so until the baby’s born. Right? Of course, if you had an amnio the day before the baby was born, and you have to wait for two weeks for the chromosomes, you might … right? So yeah, I’ve had situations where people say, “Oh, I did this test okay. I thought I was going to be one of those that had a positive result and I wanted reassurance.” And, “Oh, I’m not going to have an amnio now, but maybe after 28 weeks, or maybe when the risk of loss is lower.” Right? So people sometimes have them later. Less common, because obviously most people who do an amnio are doing it because they need to know earlier on in the pregnancy. But not always. Good. Sometimes we find things late in a pregnancy that we didn’t see or there are challenges with baby growth and so, on occasion, we’ll have a good clinical reason to do one also later.