In part two of this episode, Dr. Kelly Zafman and Dr. Fox continue their discussion of antepartum testing. Dr. Zafman explains nonstress tests, which compares a baby’s heart rate with contractions. She also reviews the biophysical profile, or BPP, as well as a modified biophysical profile.
“Antepartum Fetal Testing, Part 2: Nonstress Test & Biophysical Profile” – with Kelly Zafman, MD
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Dr. Fox: Welcome to today’s episode of “Healthful Woman,” a podcast designed to explore topics in women’s health at all stages of life. I’m your host, Dr. Nathan Fox, an OBGYN and maternal-fetal medicine specialist practicing in New York City. At “Healthful Woman”, I speak with leaders in the field to help you learn more about women’s health, pregnancy, and wellness. Let’s move on now to specific tests that we might do in the office. And let’s start with the nonstress test or NST. So, what is the nonstress test?
Dr. Zafman: So, the nonstress test and, you know, we call it the nonstress test, but usually it is a bit stressful for people. What it is, is basically placing the baby on the heart monitor, and then placing the other monitor on the uterus to measure contractions for 20 minutes, and we’re looking to see the baby’s fetal heart tracing. And there have been kind of accepted parameters of what we think that a baby, at certain gestational ages, whether it’s 28 to 32 weeks, 32 weeks to full-term, what it should look like. And really, it looks like we’re really reading like squiggly lines, essentially, because that’s exactly what we’re doing. So, we’re looking for a few different things. One of them is called variability. So, looking in kind of the beat-to-beat variations of the baby’s heartrate, and then also looking for accelerations, which are kind of like an uptick in the baby’s heartrate.
And the idea here is that we think that babies respond to, you know, things that are going inside the uterus, whether it’s their own movement or something that’s happening on the outside, and a healthy baby should kind of have those signs that we’re looking for on the fetal heart tracing. We kind of have these accepted numbers that we use, and generally, we do it for 20 minutes. If we don’t see those two upticks that we’re looking for, sometimes it can be 40 minutes and then we kind of, you know, think about different sides that the babies can show us. If they’re low fluid, and we’ll kinda get to the other test, which is a biophysical profile. But that’s kind of the general sense of what the nonstress tests look like.
Practically, for women, what that looks like is you come into the office, and you sit in usually what looks like a comfortable chair… I remember, as a medical student, I felt like it looks like one of those massage chairs in, like a nail saloon but you get to relax in the chair and you get placed on the monitor. And then you have a nurse that usually places women on the monitor, and then you have someone reading that tracing in real-time and kind of making decisions about what the next step is, depending on what that looks like.
Dr. Fox: Yeah. And I think a lot of women might be sort of used to this or have seen this before because it’s the same kind of monitoring we do conceptually for women in labor.
Dr. Zafman: Yeah, exactly.
Dr. Fox: You know, the difference is…well, there’s many differences, obviously, but one of the main ones is a nonstress test…and the reason it’s called nonstress, it’s because there’s no stress for the baby, meaning it’s not done when a woman’s in labor, a nonstress. It’s meant to be when the baby’s at resting state, there’s no contractions going on, there’s no bleeding going on, it’s just…you know, this is what the baby’s like at rest and that’s why it’s called nonstress. And yes, it is stressful for the mother, non-stressful for the baby. So, that’s why it’s called the nonstress test.
But the two discs on the belly is the same as when someone’s in labor, one’s measuring the heartrate, one’s measuring the contractions, if there are any. And it’s really interesting because, you know, you mentioned the word squiggly, which I love. That’s my favorite word for nonstress tests, and monitoring, and labor. You know, the principle is that…let’s say we measured someone’s pulse over time, right. You know, you have a little pulse monitor, and it’s beating and your pulse is 80, so it’s 80, 80, 80, and you’re just sitting there at your desk doing work, or watching a movie or reading a book, whatever. It’s basically gonna be the same continuously. So, if you charted over time, it’d be a flat line at 80, right. At minute 0, it’s 80, at minute one, it’s 80, at minutes 2, it’s 80, it’s always 80.
Now, if you, let’s say, got up and went for a jog, it’d be 140, and maybe if you’re sitting and someone dumped you in an ice bath, it would go down to 60. But basically, it’s gonna be the same and that’s normal for adults, but fetuses don’t do that, because the fetal brain is still developing. And so, there’s this push and pull on the heartrates, you know, part of the fetal brain’s making it faster, part of it it’s making it slower. And so, the fetal heartrate at rest is not just…first of all, it’s faster, it’s not 80, it’s between 120 and 160, usually, or 110 and 160. But it’s also all over the place, right. It’s 120 at 1 second, and it’s 140, then it’s 130, then it’s 125. And so, it’s all over the place, and that’s a healthy sign.
And in fact, it’s the opposite of adults. If a fetal heartrate is, like, 120, it’s just continuously at 120 beats a minute even though it’s beating, right, baby’s alive. Heartrate’s beating fast, 120, that’s not a good sign because that’s a sign that there’s low oxygen to the baby. So, when we do this test, and we see a squiggly line, we have pretty high confidence that the baby’s getting oxygen because that’s what’s supposed to happen. And then when you mentioned about the heartrate jumping up, these accelerations, that’s sort of like…think if you see a newborn just lying there, and occasionally, they just sort of, like, startle and they sort of, like, you know, move, and their heartrate jumps up, and that’s true with fetuses. They’re supposed to do that also, it’s a sign of good oxygen. So, if you see a squiggly line, and you see the heartrate jump up, we’re highly confident the baby’s getting enough oxygen. But the nonstress test won’t tell you anything, usually, about is the baby getting enough food or water, right?
Dr. Zafman: Right. Exactly. And that’s kind of where the biophysical profile comes in.
Dr. Fox: Right. So, the nonstress test is used, and it takes at least 20 minutes up to 40 minutes. And again, if it’s reassuring, it’s great, but if it’s abnormal or not reassuring, the problem is most of the time that baby’s still fine because the babies are sleeping, all right, and their heartrate’s there and it’s just not jumping up. Most of the time, the baby’s still okay, but we have to move to the next step. The next step after a nonstress test is usually what we call a biophysical profile. And some people just start with the biophysical profile, which we’ll talk about. So, what is the biophysical profile, the BPP?
Dr. Zafman: The BPP is sort of based on ultrasound. So, now we’ve moved from, you know, being on the monitor to an ultrasound portion of the test. And what we’re looking for is a few different signs that can give us a little bit more information about how the baby is doing, in terms if it’s, you know, receiving oxygen and fluid from the mom. And so, we are looking for a few different things. One of them is the baby’s movements. So, we’re looking for big movements of the baby flexing and extending its spine. We’re looking for tone, which we can also look for a movement and the baby doing small movements, like opening and closing its fist. We’re looking at the fluid around the baby, and then one of the coolest things, I think, is looking for fetal breathing, which I think can be confusing for patients.
So, babies aren’t, you know, obviously, getting their oxygen through breathing on the inside. All of that is coming through the placenta, through the umbilical cord, and from mom to the baby, like we talked about. But babies do have muscles like the diaphragm, which they start to practice using on the inside. And so that practice breathing can look like babies actually breathing, but, obviously, that’s not how they’re getting their oxygen. But those are kind of the signs that we look for to tell us that baby is, you know, getting that amount of oxygen and fluid to tell us that it’s doing well in there.
The cool thing is that hiccups actually count as breathing, which I think is fun. But you get two points for each of those things. I’m not exactly sure why everything is two. I guess somebody wanted their baby to be a perfect 10, but you get 2 points for each of those things, and then the nonstress test also counts as 2 points. So, you get overall those five things that we talked about. Each of them is 2, and so perfect score is 10 on the biophysical profile, and you get 30 minutes for that ultrasound.
Dr. Fox: Yeah. I think that the reason it’s 10 points, is I think when it was invented, they wanted it to mirror or mimic the Apgar score, where the best score was 10 also. And so, they did five things, two points apiece. The odd thing is you can’t get a one, you get a zero or a two.
Dr. Zafman: Right. There is no half credit.
Dr. Fox: So, the scores are either 0, 2, 4, 6, 8, or 10. Apgar scores, you can get, you know, odd numbers. So, I don’t know, it’s whatever, it is what it is, that’s just sort of the scoring. And the biophysical profile, like you said, the full biophysical profile includes a nonstress test, plus four ultrasound components at two points apiece, three of them are related to the baby’s movements. So, if you see those three movements, again, babies that are moving are getting good oxygen, but this one actually measures the amniotic fluid. And so, you sort of get the next level of testing, in addition to the baby’s getting enough oxygen, that the baby’s getting enough water, and why is it that the level of amniotic fluid around the baby tells us that the baby’s getting enough water through the placenta?
Dr. Zafman: Yeah. So, because amniotic fluid is essentially baby pee, we think that if babies are getting sufficient water through mom that they’re gonna produce more fluid. And so, if we’re worried about the way that the placenta is functioning, a lot of times that can be reflected in having decreased fluid, which we call oligohydramnios. And sometimes that, in itself, can be sort of a key that our placenta is not functioning as well, or something is going on that is preventing the baby from getting adequate fluid.
Dr. Fox: Exactly. And so, it sort of gives us another additional layer of testing for the placenta because, again, the nonstress test was is the baby’s heartrate sort of pattern indicative of the baby having good oxygen. And when we do the movements, again, same thing, a baby that’s moving well is because the baby’s well-oxygenated. But now that we add the fluid measurements, it gives us sort of the next level that the baby’s getting enough water through the placenta. What you mentioned about breathing is really interesting, and I always tell women the same thing, I’m like, “Your baby’s an underwater creature, right, inside.” They live underwater, they don’t need to breathe, they’re like the deep-sea divers with, like, the oxygen, it comes into their belly button. Like, they don’t need to get any oxygen through moving their diaphragm up and down, but they do. They practice it, it’s really fascinating. And you watch it on ultrasound, you see that diaphragm moving up and down, and up and down, and they don’t do it continuously, they do it in spurts.
And that’s the main reason often this biophysical takes 30 minutes. Usually, the movements we see pretty quickly, but that breathing, you gotta catch it when it happens. And so, in a 30-minute period, it may only be moving for 5 of those minutes. And so, you gotta catch it for about 30 seconds to get all those points. And the biophysical, we said it can be a follow-up to a nonstress test, meaning either you can say, “All right. I’m gonna do a nonstress test, and if it’s normal, you’re gonna go home.” And if it’s “abnormal”, we’ll do the other components of the biophysical, and if everything is fine…so now you’re 8 out of 10, which is generally reassuring. In our office, we usually just start with the biophysical. Again, that’s just logistics. Some people find it easier to set up nonstress testing, some people find it easier to set up biophysical profiles, a lot of is how many ultrasound machines do you have. How many sonographers do you have? You know, there’s reasons to pick one or the other. There’s some data differentiating the two of them, but ultimately, reassuring test for each of them is very reassuring. It doesn’t make a huge difference which one you do from a medical standpoint. What do you guys use at Penn?
Dr. Zafman: We do nonstress first.
Dr. Fox: A lot of hospitals do nonstress first. I think there’s more space and there’s usually a room with, like, four, five, or six, you know, beds or recliner chairs and one nurse who runs it. Is that how you guys have it there?
Dr. Zafman: Yeah, exactly. I feel like a lot of it is just space issue, honestly, because with the ultrasound they have to get individual rooms and here we can kind of have people, you know, set up in one big room, but obviously, every place, you know, has its own practice. But, yeah. The reassuring thing is that we know that both of them, you know, ultimately get us to the same outcome.
Dr. Fox: Right. And there’s also a quick and dirty way to do the nonstress test and biophysical, and that’s something that we call the modified biophysical profile. Do you guys use that at all?
Dr. Zafman: We do. Yeah.
Dr. Fox: Yeah, so explain what the modified biophysical profile is.
Dr. Zafman: So, with the modified biophysical profile…I mean, I think people do it a little bit differently but I think that because the fluid is really that piece that you don’t get from just the nonstress test alone, you can do the nonstress test and do, like, a fluid measurement to give a kind of a quick and dirty sort of indication that, both from fetal heart tracing that things are doing well and then also from a fluid standpoint that things are looking good. So, often, our patients will get twice weekly nonstress tests, and then once a week, we’ll do a check of the fluid as well. And if babies happen to be breathing or moving during that point, they’ll get points for that too, but they won’t spend extra time doing that as long as the nonstress test is good.
Dr. Fox: Yeah, because it’s easier to check the fluid. Like, if you’re doing an ultrasound, it’s pretty easy to measure the fluid because you don’t need the baby to do anything, right. You just go in there and you find the fluid pockets. Either you measure one pocket or you measure four pockets, you know, there’s different ways to do it. And we have our podcast on fluid, we’ll talk about that. But it’s not complicated to measure the fluid. And so, you can really have any one. If the nonstress test is normal, and the fluid looks good, it’s almost the same thing as getting a full 10 out of 10 on the biophysical because if you have those accelerations on the nonstress test, you’re basically 100% sure the baby’s moving to some capacity because they move during those accelerations. So, it’s like… that’s why it’s called modified. It’s almost like doing a full biophysical profile without having to spend 30 minutes on an ultrasound machine, potentially. I think a lot of places do that, because like you said, from the nonstress test, you couldn’t really assess the fluid, but with the modified biophysical or the full biophysical you can. Now, in all of these scenarios, we have not mentioned any way to assess if the baby’s getting enough food. And so how do we do that?
Dr. Zafman: Yeah. So, that really comes with growth ultrasound, which, you know, carries its own host of things but essentially, you can do a growth ultrasound where you are measuring different sort of parts of the baby, you measure two different measurements in the head, a measurement of the baby’s abdominal circumference, kind of a measurement around the waist, and then also the femur length. And there are different formulas that we use, but typically people use the Hadlock formula. And that gives you an estimated fetal weight.
You know, obviously, you have to take those things with a grain of salt because all we can do is take those measurements and put them in a formula, and, you know, there’s about a 10% to 15% margin of error in either direction. So, it’s definitely not an exact science, but it’s one way that we have to measure how the baby is growing and making sure the baby is getting, you know, the food that it needs from the mom.
And because there’s that margin of error, you know, we don’t wanna do them too close together because we could, you know…if we do an ultrasound one day and then do one the next week, we might see that the baby’s, like, shrinking or something, which does not happen, which would make people really worried. But really, it could just be that, you know, we’ve measured, oh, a teeny bit off here, a teeny bit off there, and then because of that, we’re still within that margin of error. So, I think lots of times women are like, “Oh, why aren’t we measuring the baby more often?” And it’s really because we wanna give that time for baby to grow so that we can really see significant differences and tell us about how the baby’s growing in terms of its trajectory.
Dr. Fox: Yes. And I think pretty much anybody who’s gonna be undergoing this antepartum fetal assessment is also gonna be getting some form of a growth ultrasound at some interval. Like you said, it’s gonna be less frequent than the testing. So, whether the testing is once a week or twice a week, checking the baby’s weight is every two weeks, three weeks, four weeks, eight weeks, something in that range. But that’s the way we assess how the baby’s getting enough food. So, that covers food, water, and oxygen. Now, there’s a couple of other tests that are done less frequently, something called a contraction stress test, or a CST. So, what’s that?
Dr. Zafman: So, what that is, it’s kinda similar to the nonstress test, but here, we’re actually doing things to bring on contraction. And so typically, you know…I don’t know how actually they do it at [inaudible 00:16:16] but at Penn, what we do is we’ll admit women to the labor floor and either use nipple stimulation, or Pitocin to bring on contractions, and then basically see how the baby does with those contractions. And what you’re looking for is sort of dips in the heartrate with contractions, that would be sort of a sign that baby’s not tolerating the contractions as well. And then depending on, you know, sort of the clinical scenario and the gestational age, you might actually think, you know, maybe it’s actually time to deliver the baby.
So, like we said, for the nonstress tests, you know, the baby’s under no stress, we’re just kinda seeing how it’s doing in its natural environment. But here, we’re actually putting a stress on the baby. And oftentimes, that tells us a little bit about the way the placenta is functioning. So, if we’re sort of worried that a baby is not really going to tolerate contractions, sometimes that tells us that maybe it’s time to deliver the baby. And, you know, sometimes we’re able to still, you know, recommend an induction, but, obviously, knowing that if the baby’s already showing signs of trouble tolerating contractions, there is a little bit of a higher risk of a C-section, or depending on what’s going on, sometimes we might even outright recommend a C-section, depending on the situation.
So, in that, you know, situation we’re a little bit, you know, concerned that if there’s some issue with the placenta, you know, typically a baby’s able to tolerate contractions just fine. But if we’re already worried about the placental functioning, and now you added stress on top of that, sometimes babies just aren’t able to tolerate that as well.
Dr. Fox: Yeah. I mean, this isn’t done as frequently, it’s not… I wouldn’t say a routine test, it’s sort of done case by case for someone who you wanna get that information…because it does involve some stuff that has to be done to get her to contract, right? You mentioned either nipple stimulation, there is a very interesting pathway physiologically for women. And that’s sort of borne out from nursing that when women nurse and there’s nipple stimulation, the brain releases oxytocin, which is something that helps for nursing, but it also causes uterine contractions, which is a reason why when a lot of women are nursing, they have cramps at the same time.
But it can be a way to sort of induce some contractions, typically not labor, but contractions that can be used for this test, or you can give them an intravenous line and actually just give them some oxytocin or Pitocin, which is another way to do it. We don’t do it that much. It just doesn’t come up so frequently. And like you said, if it’s an abnormal test, either you’re gonna recommend delivery by inducing labor, but then knowing that you may end up with a C-section because you know the heartrate’s dipping periodically due to these contractions, or just recommend a C-section.
The way I sort of explain it to people is sort of similar to, like, if you went to your cardiologist or internist and you had, like, an EKG, like, a resting EKG that’s sort of similar to the nonstress test, and then they throw you on a treadmill for 20 minutes and repeat the EKG, that’s sort of like the contraction stress test. And it tells you different things, right. Your heart pattern might be perfect when you’re sitting on a chair, but if you get on a treadmill and you have chest pain and EKG changes, that sort of tells them, “All right, even though they’re fine at rest, there’s something going on here.” And it’s the same thing with the contraction stress test for fetuses. And then what about umbilical artery Dopplers. So, what is that and when do we do it?
Dr. Zafman: Yeah. So, umbilical artery Dopplers are looking at the blood flow through the umbilical artery. And so, if we think back to kind of the physiology of what’s going on, we have, you know, the uterus, we have the placenta, which is interfacing with the uterus, the umbilical cord coming from the placenta to the baby, and the umbilical vein is what carries blood from the placenta to baby. And then the umbilical artery is what carries blood from baby back to mom.
And looking at the umbilical artery tells us a little bit about what’s going on with the placenta. So, normally, the placenta is a kind of low a resistance system. And so, baby is able to very easily bring blood from itself back to mom, and there’s no resistance. As that resistance increases, the umbilical artery starts to show us changes. And so really, what we’re doing is we’re looking to see how the placenta is functioning. To go back a bit, the reason why we might do umbilical artery Dopplers is specifically the time that it comes up is in babies who are growth restricted or measuring less than a 10th percentile. And because a lot of times, you know, as we talked about when babies are small, it’s a sign that babies aren’t getting as much food.
And so, this is one of the tests that can give us a little bit more information about how the placenta is working, and how the baby is doing when it’s measuring small because that is one of the things that can increase the risk of stillbirth, especially if babies are extremely small, like, less than a third percentile. So, looking at the umbilical artery Dopplers, like, gives us a sense. And so, you know, it can show us different things. Sometimes it’s elevated, sometimes it even reverses. So, instead of going from baby to mom, it actually goes in the opposite direction, that can tell us the placenta is starting to get quite sick. And so, it kind of gives us a little bit more information about how the baby is doing and how the placenta is functioning.
Dr. Fox: Yeah, that’s a really good explanation. You’re very talented, by the way, which I knew, but now our listeners are learning. So many people get confused when we’re doing these Dopplers because you would think, right, “Oh, they’re measuring the blood flow to the baby, right.” We want good blood flow from the placenta to the baby. And so, you would think we’d measure flow in the umbilical vein, but we don’t, it’s the opposite. We’re measuring blood flow from the baby to the placenta. And like you said, the reason we do that is it’s a really good test of the placenta because we’re not really doing it to test the baby, we’re doing it to test the placenta.
And so, if the placenta’s really healthy, the blood’s just gonna flow right through it like a sponge. And we can see those patterns. And if it’s gonna be an unhealthy placenta, we see that sort of backup, that resistance, like you talked about. And again, this is not a primary type of test we do for fetuses. And really, we almost never do it, unless we’re worried about the baby’s growth. It’s not done, like, because a woman just has diabetes, or high blood pressure, or twins, or something like that. It’s really meant to be done in a setting of if the baby’s measuring small. But it’s something that sometimes women will get, you know, once a week or twice a week, based on the specific circumstances. Now that we’ve covered all the tests, in general, what happens if it’s normal, reassuring? And then the second question is, what happens if it’s not normal?
Dr. Zafman: So, if it’s normal, then you pretty much continue testing. And so, like we talked about, you know, the time to initiate test and how often we do the test, can kind of vary based on, you know, why we’re doing the test, and then also just the institution and their policies. But typically, you’re doing the test once or twice a week. And so, you can kind of resume going back to that next test in, you know, the next few days or in the following week.
If the test is abnormal, you know, this is where things get a little bit interesting. And some of it depends on sort of the gestational age of the, you know, pregnancy, and also why we’re doing the tests, and also what portion of the tests was abnormal. And we talked about if the nonstress test is abnormal, often we’ll do the biophysical profile. And also, if the biophysical profile is abnormal, sometimes we’ll do the nonstress test.
But generally, you know, if a baby is full-term and we’re seeing things that are abnormal, a lot of times the recommendation will just be delivery because we’re already starting to see signs of maybe a placental issue, or maybe the baby’s heartrate is showing us signs that maybe there’s an issue with oxygenation. And so, a lot of times, you know, our recommendation will be delivery.
The tricky thing is when we’re not full-term, you know, of course, you know, we don’t wanna deliver a baby unnecessarily. Things like, you know, preterm delivery carry their own host of issues but if they really seem fine, sometimes we might even recommend delivering earlier, or we might recommend, you know, keeping a woman on the labor floor for additional monitoring, maybe during a growth ultrasound if she hasn’t had one in a while. That could explain sort of some of the changes that we’re seeing, but a lot of times it’ll depend on sort of the reason why we’re doing the test, and then also, the gestational age that, you know, you’re getting that abnormal test result.
Dr. Fox: Right. And also, how abnormal it is, right? There’s things like in a biophysical if it’s…everything’s perfect, but we don’t see the breathing, almost always everything’s fine, right? You do this, you do that, and it’s usually okay. But if the baby’s, like, totally not moving, and the fluid is low, that’s a very serious situation. And so, in those situations, you may deliver even preterm. So, there’s a lot of variation in this, and it’s generally, like you said, based on how far pregnant are you, meaning, how big of a deal is it “to deliver”, and how abnormal is the testing.
And one of the things you mentioned is so true, and you said this earlier as well, that one of the difficult things about this is, let’s say someone comes to my office, and she has hypertension, and she’s getting, you know, weekly testing for this and everything’s fine, everything’s stable, and then in the 38 weeks, we notice an abnormality in the biophysical, with nonstress test. Again, nothing major, but something, and we make a decision. All right. You know, you’re 38 weeks, we were gonna induce you next week, anyways, let’s do it now, we induce you. And everything comes… you know, you induce the labor, everything’s fine, she delivers and the baby’s healthy. We don’t really know did we do that unnecessarily, right. Was it a false scare, and everything was fine and we’re just being, you know, like, annoying doctors? Or did we save the baby’s life?
And you can spin it any way you want, but we just don’t know the answer to that question. It’s very hard to know, for sure, did we do something unnecessary, or did we do something that was huge in a good way and what percentages those are gonna be. Is it 90-10? Is it 80-20? Is it 50-50? It’s very hard to know that answer. And so, a lot of times you’ll hear these stories, someone says, “Oh, my doctor thought there was a problem, and they delivered and everything was fine. The doctor’s an idiot.” You know, yeah, maybe, you’re right. May be true. Maybe we just had an abnormal test that was false and we didn’t need to do any of this stuff. On the other hand, you could tell the story, “Well, maybe the doctor saved my baby’s life and we just don’t know.” And so there has to be a lot of humility with this testing when we do it, that we’re just talking about managing risk and trying to optimize outcomes and doing our best, but we don’t always know on an individual person if this is helping, by how much, in what situations. And it’s tough, which is why there’s a lot of art in this, in doing these tests.
Dr. Zafman: Yeah, it kinda takes me back. Like, my intern year, I remember I was on the Maternal-Fetal Medicine Service and we had a patient who had a nonstress test that didn’t have the uptick, meaning it was not reactive. And so, she had to have a biophysical profile, and I did it. And she got a 2 out of 10, and then ended up with a stat C-section. And I remember the baby came out kicking and screaming, and, you know, I was like, “Oh, my gosh, did we just deliver this baby early, you know, based on this test that I did?” And the problem is that you just never know. You don’t know, like…you can only know what happened in that moment, you can’t kinda see the alternate universe of what would’ve happened if you kept someone pregnant. So, I think it is… like you said, it’s kind of, like, humbling, and also tricky, you know, to be able to make these recommendations off of, you know, just the information that you have in front of you.
Dr. Fox: Right. But it’s also part of the reason we try not to do these tests, except for women who have risk factors for stillbirth because if you start doing them routinely on everybody all the time, you’re gonna sort of, for sure, build up enough false scares that you are gonna be delivering people early, or unnecessarily because there was a very low risk of stillbirth at baseline. And so, we try to reserve them for women who have some increased risk at baseline. So, at least there’s, like, some logic to this, why there would be an issue. And again, that comes…it’s all, like, the math and statistics behind these testing and who gets it, who doesn’t. That’s sort of the principle that you start with a population that’s already an increased risk, has some increased anxiety, that’s legitimate. And so, an abnormal test probably means more than if you did it in people who just have nothing going on and everything’s fine.
Dr. Zafman: Right. And then I think also the question comes up, you know, when to start testing, you know, because, in those days, people say, “Oh, is it 28 weeks, 32, 36?” And kind of the fear is that we know how, you know, babies that are a little bit older are supposed to behave. But if you gave an earlier baby a test, like, you’re basically giving a kindergartener a test that’s meant for a fifth grader. We don’t know if the baby doesn’t do well because of the baby or if it’s because it was the wrong test for them. So, again, it gets into a lot of the nuances about when to start the testing and how often to do it and for who.
Dr. Fox: Yeah, no, I totally agree. I think, for our listeners, some of the takeaway messages are these tests are common. A lot of women have risk factors for stillbirth. That does not mean that there’s something horribly wrong with them, but they’re done commonly. There’s a bunch of different tests and which one is chosen is usually an issue of logistics, more of specifically tailoring something medically, right, because they pretty much have similar efficacy that we know about. And an abnormal test does not mean definitively there’s a problem. It just means we either need to investigate further or maybe you’re far enough along in pregnancy that, you know, it’s not worth the investigation, you know, because we might be wrong. It’s better off just delivering.
And that a normal test is not a guarantee, but it’s very reassuring, at least, in regard to the placenta, that the placenta health, at that time, is normal and none of this is supported by amazing evidence, which is why people do it differently, but it’s not out of nowhere. Like, there is a lot of physiology behind this, there’s a lot of research behind this. And so, I wanted to talk about your study for a little bit, just what you looked at because A, to plug you as a researcher because you’re awesome. And, B, because, again, it’s an interesting way to look at something that’s slightly different from what we just spoke about. So, tell us what you looked at in your study.
Dr. Zafman: In our study, we were looking to see what the outcomes were in your ultrasound unit where the standard of practice is to have women do once weekly biophysical profiles, instead of the nonstress test. So, here, our sort of perfect score is gonna be an eight out of eight because we don’t have the nonstress test components. And we’re basically seeing, you know, is this an effective way to be able to screen women. There’s been a lot of data that suggests that it is, but it hasn’t been done in big numbers and in this patient population. So, we were specifically looking at women who are already getting biophysical profiles for maternal reasons. So, we didn’t include the, you know, babies that were smaller or had other issues. We were literally looking at, you know, women who have risk factors for stillbirth, things like we talked about, like diabetes, high blood pressure, lupus, and look to see sort of what were the outcomes in those ultrasounds and in those pregnancies. And so, we looked at a big number of women, and because like we said, stillbirth is rare so you need to use big numbers to be able to see these outcomes.
And so overall, it was from 2006 to 2018, and we looked at 985 women who had about 4,000 ultrasounds for those maternal indications. And we look to see, you know, what were the rates of positive tests, and what were the outcomes that we saw. So, overall, in those 4,000 ultrasounds, only 16 of them were positive. So, only 16 women had abnormal tests on the biophysical profile. So, the rate of that positive result was 0.4%, so pretty low. And then the question was, you know, what happened to those women. So, 13 of them, ultimately, got delivered for an abnormal test. Three of the women who didn’t get delivered at that point had normal nonstress tests. So, they had the abnormal biophysical profile, they got sent to the labor floor and had a nonstress test at that time. And so those three women continued on their pregnancy and delivered later on, and all had great outcomes. And those 13 of 16 women who got delivered for their abnormal tests on the biophysical profile, also had great pregnancy outcomes, no complications there.
There were, you know, unfortunately…you know, we’re studying a big population of women, and who all have risk factors. There were three women who had a stillbirth. And so, overall, that rate was extremely low, was 0.3%. Those women did have biophysical profiles that they had been done. Two of them had it done a week out from the diagnosis of a stillbirth. One of them had it six days out and all of them had, you know, significant risk factors. But you know, of course, that’s devastating. But the good news was that it was very low, so only 0.3%, which is actually the same or even lower…you know, that’s kind of, like, a false negative, if you will, where the test says that the baby, you know…and like we said, we’re not exactly testing the baby, and not for all the reasons for a stillbirth. But we had signs on the biophysical profile that the placenta was working well, that the fluid was normal, and they, unfortunately, ended up with a stillbirth. But the good news was that it was about the same, or even slightly lower than we would expect with the nonstress test. So, it told us that this is definitely, you know, a reasonable and practical way that we can do antenatal testing and still end up with really great outcomes.
Dr. Fox: Now, great summary of your research, and I love that you did this study, and published it. Now, when you’re sort of at Penn, do people approach you and say, “Hey, you’re Kelly Zafman, you’re the famous publisher on this topic, you know. Tell us how you do it.” Does that come up a lot? Are people asking for your autographs around there? Like, how does that work?
Dr. Zafman: Not quite yet. But, you know, I think that it’s, you know, helpful to look into this because, you know, like we said, there’s not a lot of really great big studies on this because women are not going to… you know, we can’t really tell people like, “Oh, we’re not gonna test you.” I think this is the only really way right now that we have to say that these are tests that we can use to promote good outcomes in women. And so, I think it’s really reassuring, and I think a lot of times it, you know, is a way that we can, you know, counsel patients. It can be really hard for them to come to all of our testing, and I think this kinda shows the importance of it because when we do a test, we end up with really great outcomes. So, I think it’s useful for patients to be too…like, you know, we’re not just asking you to do this stuff, you know, because we’re trying to torture you with all of your appointments, but because we really do think that it, you know, helps us in our outcomes.
Dr. Fox: Kelly, great. Thank you so much for coming on the podcast. And I wanted…
Dr. Zafman: Thank you for having me.
Dr. Fox: It’s my pleasure. We’re, for sure, gonna have you back, we have to talk about growth ultrasounds because you mentioned that and that’s something you also did research on and we both have spoken a lot about this in the past and looking at this, so we’re gonna do that. And I also wanna commend you, because, you know, you spent a full hour plus talking to me, and you’ve successfully avoided having to decide whether you were gonna me Dr. Fox or Natty, which I love. And I know this, and I’ve been thinking about it the whole time and I know that you’re probably thinking, “What do I do? What do I do?” And I think that’s great. So, good work, avoiding my name the entire time.
Dr. Zafman: It’s kind of like when you’re a kid and you don’t call your friend’s parents anything because you don’t know what to call them, so you’re just like, “Excuse me, ma’am or, you know…”
Dr. Fox: For the record, for all our listeners, anyone on Earth can call me Natty including Kelly, but I know that she’s a little bit shy on that regard, and that’s okay. That’s a lovely sign of respect that’s unnecessary and unwarranted. But it’s good, and I just love feeling the stress in your life trying to figure that one out for the air. Good stuff.
Dr. Zafman: Thank you so much for having me. I really appreciate it.
Dr. Fox: Thank you for listening to the “Healthful Woman” podcast. To learn more about our podcast, please visit our website at www.healthfulwoman.com, that’s healthfulwoman.com. If you have any questions about this podcast or any other topic you would like us to address, please feel free to email us at firstname.lastname@example.org. Have a great day.
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