“Vasa Previa: The critical importance of diagnosis” – with Dr. Andrei Rebarber

Dr. Nathan Fox discusses vasa previa with Dr. Andrei Rebarber, Maternal Fetal Specialist and a founding physician and President of Maternal Fetal Medicine Associates and Carnegie Imaging for Women. This serious pregnancy complication can cause risks to the fetus, though early diagnosis and careful monitoring with a scheduled C-section improve the odds of optimal outcomes.

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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. All right, Andrei, Dr. Rebarber, the great Dr. Rebarber, welcome back to the podcast. How goes it?

Dr. Rebarber: Good morning. It’s been a while.

Dr. Fox: It’s been a while since we podcasted, and we are in different offices.

Dr. Rebarber: But I do I see you every day.

Dr. Fox: Yes, yes. As I’ve said multiple times to many people, I have a wife and I have a life partner, and that’s you. But today we’re far away. You’re in New Jersey, I’m in New York. We’re over the phone. We’re not face-to-face. So be it. That’s how the schedule God’s made it. That’s how it’s gonna be.

Dr. Rebarber: We can never be at the same location at the same time for safety of the practice.

Dr. Fox: For security reasons, you know?

Dr. Rebarber: Exactly.

Dr. Fox: All right. Well, that’s good. So, well, we are secure. The Secret Service has you in an undisclosed location, just in case, you know, I get mugged in the street today. Cool.

Dr. Rebarber: President and the Vice President.

Dr. Fox: Exactly. Well, it’s more like you’re the president, and I’m like, I don’t know, the Secretary of Agriculture, or something like that. I don’t think I really…

Dr. Rebarber: No, it’s really the other way around. All good.

Dr. Fox: All good, indeed. All good. So I picked the topic for today, which is vasa previa, which is…it’s somewhat of an esoteric topic, meaning it’s not really relevant to a lot of people or to most people in their lifetime or in pregnancy. But I think it’s something that a lot of people don’t know about and it’s really important, and this is true for patients, for doctors, it just gets overlooked for some reason. But it’s a big one.

And this is something I know that you are very interested in. You’ve done research on this, we’ve done research on this, and I think that it’s worthwhile to sort of explain what it is and help people through this so they sort of understand it and get it and maybe find out if they should be screened for it. So, yeah. Can you just explain broadly to our listeners what exactly is vasa previa?

Dr. Rebarber: Yeah, I mean, so it’s, I believe, Latin root. Vasa means vessel and previa means low. And so it basically implies it’s a low vessel. What it is, it is really a fetal blood vessel that’s present in the membranes in sort of between the amnion and the chorion that covers the cervical opening or is adjacent to it. The definition sort of originally of it covering the opening of the cervix sort of predates ultrasound and ability to diagnose it prenatally.

And it was recognized traditionally by either palpation during examination or visualization as the cervix dilated. And it was rarely ever identified prenatally because, again, ultrasound is the only way to pick it up, and there was a lot less access to good ultrasound. And then, additionally, it can be quite catastrophic if it gets missed, though is quite, quite rare. And we do know there are risk factors for people who develop this. So we sort of guide our focus in identifying it on patients with some risk factors.

Dr. Fox: For our listeners trying to sort out like how does a fetal blood vessel get in front of the cervix? Like, where are they normally? It’s definitely confusing in a sense, and the way I try to explain it to people is normally the baby is connected to the mother through the placenta, right? So the baby has this umbilical cord that comes out of his or her belly button, so to speak, and it travels towards the placenta. And in that umbilical cord are three blood vessels.

There’s two arteries which bring blood from the baby to the placenta. And there’s one vein which brings blood from the placenta to the baby. And normally, that cord sort of plunks right into the middle of the placenta, and that’s it. And we’ve discussed in the past when the placenta itself covers a cervix, which is called the placenta previa, a lot of people have heard of that.

A vasa previa is sort of two things have to happen. Number one, there has to be sort of an abnormal or unusual connection between the baby and the placenta where the cord doesn’t plunk into the placenta, but it sort of plunks into the membranes to the side of the placenta and then those blood vessels in the cord have to sort of travel along those membranes to get to the placenta. So that’s sort of thing number one that has to happen, which, itself, whatever.

And then number two is coincidentally that area where these blood vessels are sort of just traveling along the membranes on their own, not on the cord, has to also be in front of the cervix. There’s times when it happens and it’s not near the cervix, which is its own issues, but when it’s in front of the cervix, that’s what we call a vasa previa.

And so, again, since those things both have to happen, it isn’t very common like you said. I mean, what would you guess? I mean, it’s less than 1% of the time. What would do you tell people sort of the incidents or the likelihood from scratch that someone’s gonna have this in pregnancy?

Dr. Rebarber: Well, it’s actually been reported as low as like 1 in 1,300 to 1 in 2,500. So it’s actually well rare, but just to sort of talk about there actually are three types of this. And one of the types is, as you described, with developmental cord insertion or marginal umbilical cord, so the umbilical cord seems to insert on an edge of the placenta and then it sends out a vessel that’s near that.

But there also are, you know, type two where you actually have what’s called a bilobed placenta and/or succenturiate lobe. So there’s an extra lobe, the placenta ends up, instead of one plate, two plates. And then you have this membrane, sort of connecting vessel that occurs within the membranes itself between them, and that happens to be over the cervix. And then a type three more recently described has been where you have basically an otherwise normal-looking placenta, normal insertion, but then a vessel seems to kind of boomerang out over the internal oz.

And that is thought to be from a placenta previa, a placenta that was low that kind of resolved. Theoretically, we could go on how that happened, and leaves this sort of surface vessel behind over the cervix. So you have sort of the traditional and more common one, the type one which everybody knows about, which is related to this velamentous cord insertion where the cordon inserts into the membrane and then has to send out vessels to travel to get to the placenta. A marginal cord insertion type two, which is the bilobed or succenturiate, and type three, which is sort of a boomerang vessel that comes out that’s sort of less usual.

And we can map this in with ultrasound to identify where these vessels are sometimes. And so we, you know, with careful ultrasound surveillance, particularly in high-risk groups that can help to identify which type and the type of vessel it is, whether it’s an artery or a vein as well and how many.

Dr. Fox: Right. So who would be a high-risk group then?

Dr. Rebarber: So certain risk factors include development cord insertion, which is routine in prenatal care when you’re doing what we call a level two anatomy scan, even a “level one” basic anatomic survey. They should always look at the placenta and establish where the cord is inserting into the placenta. Not just the fetus, but into the placenta. So it’s normal that they focus on the fetus and fetal anatomy and fetal structures, but from the placenta itself, it’s very important to localize where it’s located and the code insertion itself. So that’s one, developmental code insertion.

And then the other issues are if you see a placenta previa or a low-lying placenta in the second trimester, either one of these names for that, particularly if it’s near…and that’s defined as covering the opening or near the opening of the cervix, that’s important to then look for this condition. If you see the bilobed or succenturiate placenta, that’s also important.

And then, finally, for… We identified and wrote up some case reports on multiple gestations, and having IVF alone is also associated with this condition, invitro fertilization, probably related to the fact that IVF pregnancies are at high risk for placenta previa, which then, obviously, results in the higher incidence of vasa previa. So these sort of five categories are probably the most common and would probably identify close to 90%, 95% of cases that have vasa previa in one of these risk factors.

Dr. Fox: When we have the podcast on placenta previa, and I’m talking about this because I wanna differentiate it from vasa previa. So when we were talking about placenta previa, so that’s where the placenta’s covering the cervix. And the concern was that if the placenta’s covering the cervix either before labor or during labor, the mother can start bleeding from the placenta, sort of having a loose attachment or detaching from that area by the cervix, and that could be predominantly dangerous to the mother, but then ultimately dangerous to the baby.

So we’re not talking about that here because this isn’t the placenta in front of the cervix, it’s a fetal blood vessel in front of the cervix. So can you explain, why is that dangerous and who is it particularly dangerous to, the mother or the baby?

Dr. Rebarber: It’s particularly dangerous to the baby, not the mother as opposed to a placenta previa, which has…both dangerous to mother and baby. What the main concern with it is, is that when labor is about to start, or if a mother breaks her water early and the sack bursts, the vessel ruptures. And if the vessel ruptures or bursts, you have fetal bleeding that’s occurring through this blood vessel because it is the fetal vessel that’s within the membranes on the surface. It should have been on the surface of the placenta, but it’s now in the membranes on the surface of the cervix. And so that can result in pretty rapid blood loss from the fetus and high association with fetal death if that were to occur.

Dr. Fox: Yeah, I mean, the fetus has very little capacity to bleed, right? If the mother’s bleeding, it’s not good. But, you know, as adult humans, particularly when you’re pregnant, you can lose a fair amount of blood and come out completely unscathed. Or if you keep losing more blood, you can get a blood transfusion and basically come out unscathed and be okay.

But if fetus’s blood volume, like at full term, the total blood volume of a fetus is about the size of, I don’t know, a can of soda, right? It’s, you know, one of the small water bottles people carry around. So the baby, if he or she loses blood at a certain point, they don’t have any capacity, and it can be lethal. And, in fact, it is lethal if unknown and they start bleeding. It’s very hard to sort of save a baby who’s already started bleeding. To do it in time is very difficult, and that’s why this is such a significant condition. What is the mortality, like if someone has a vasa previa, what’s the likelihood the baby would start bleeding and die?

Dr. Rebarber: Well, if it’s undiagnosed and you’re basically waiting, you diagnose it in labor itself, it’s actually pretty high because, again, patients break the water early or a doctor breaks the water with a what’s called an amnio hook, and that itself can result in rapid exsanguination.

So in the pre-ultrasound diagnostic era, the association was in the 80%, 90% range as far as mortality rate. It dropped with fetal monitoring in labor in the 50%, 60% range because of the fact that if it were to happen, you happen to be on the labor floor being monitored, there’s a rapid drop in heart rate and an emergency C-Section can be performed if somebody’s lucky enough to have that while they’re actually in labor and being monitored.

But it’s a pretty high… Because it happens so rapidly. In general, vaginal bleeding is maternal blood usually. This is one of the most unique cases where the bleeding that is occurring vaginally is not maternal, and its fetal blood.

Dr. Fox: And then you were gonna say in the era of ultrasound, what is it now, the mortality?

Dr. Rebarber: Oh, in the era of ultrasound, now, with prenatal diagnosis, and we have over 100 cases with vasa previa, 120 or so. We only had one twin case in which she went into preterm labor, is suspected to have had that happen. Unknowing that she had, she just couldn’t get to the hospital in time and there was a preterm birth at around 30 weeks or so. But, otherwise, only one less problem. So it’s gonna be statistically in our series under 1%.

Most of the data suggests it’s gonna be pretty low under a couple of percent if you can diagnose it prenatally because we admit patients earlier, and particularly in the high-risk groups and deliver them earlier to avoid the spontaneous onset of preterm labor or ruptured membranes.

Dr. Fox: Yeah, I mean…

Dr. Rebarber: Before labor starts.

Dr. Fox: That’s one of the biggest sort of lessons that we go over with patients if they are diagnosed with vasa previa because, you know, you can Google it and find anything, and it’s not necessarily wrong, it’s just sort of the context of what are we talking about. So, again, I tell people if it’s undiagnosed, if someone just has a vasa previa, has no idea they have it and they show up in labor, their water breaks, you know, you’re talking 50%-plus mortality to the baby, the baby’s gonna die, like horrible. It’s like it’s so unusual to have a condition that has such a high mortality for a full-term baby. But if we know about it in advance, that’s never zero, but it’s really close to zero.

And I tell them, again, less than 1% and predominantly because our goal is essentially to deliver the baby by C-section before the mom goes into labor. And we’ll talk about exactly how we do that and when we do it and there’s, you know, some nuances and that and some disagreement. But that’s the principle, if you know about it, the chance that it’s gonna end horribly is exceedingly low and if you don’t know about it, the chance it’s gonna end horribly is exceedingly high, which is why it’s so critical that we know about it. So how do we find out, how do we diagnose it?

Dr. Rebarber: Yeah. So, I mean, ultrasound is the standard two-dimensional ultrasound with specific technique called color flow that identifies the vessels, is the standard. 3D ultrasound can help, but it’s not necessarily required. The number one thing is a high index of suspicion, primarily looking at risk factors that we talked about can be very helpful.

And then, really, in those patients with risk factors, particularly routinely looking at the cervical length and then measuring above the cervix, any vessels that you see near that area and their distance to the opening of the cervix, it’d be very helpful and likely to be able to identify. The sensitivity or the ability to pick this up exceeds 90%, 95%. In centers that are more skilled to do this, like in our prenatal diagnostic unit, it’s over 99% in our ability to diagnose this.

And we’ve been screening for vasa previa now for probably since its inception in 2005 based on risk factors. And that’s why we wrote two series on screening based on risk factors and identifying it. In general, ultrasound, everybody should have a really good high-resolution ultrasound at 18 to 20 weeks. And during that timeframe, look at where the placenta is located and image the lower uterine segment in the cervix.

And this can be done abdominally or vaginally and just make sure there are no fetal vessels in that area. You just put this color flow doppler on, and that’s it. But again, particularly in risk factors, you should be looking at this, and the best way to diagnose it is transvaginally.

Dr. Fox: Yeah, I think that’s an important point that you can screen for it and look sort of abdominally because most ultrasounds are gonna start abdominally. Not everyone is gonna have a transvaginal ultrasound. In some units, they do it routinely, some units only based on certain risk factors or findings. And again, there’s pluses and minuses to both strategies.

But ultimately, I think the first thing you said is the most important thing, is that there has to be an index of suspicion for it. Meaning, the person who is doing the ultrasound has to know that this condition exists, and what are the risk factors for it, and because of that, I need to look. So, for example, if someone has placenta previa that then moved out of the way, you know, it is no longer placenta previa, it’s a pretty strong risk factor for having a vasa previa, the person is doing the ultrasound and sort of has seen this happen over time, needs to have the index of suspicion to say, “You know what, I gotta be certain that there’s not a vasa previa there,” ideally vaginally, unless they can be certain abdominally, though that’s tough to do. And then check.

And I think that if you… Because if you don’t look, you won’t diagnose it. And if you look, like you said, and you know what you’re doing, you’re gonna diagnose it. And since that is literally the difference between life and death for the baby, it’s a huge, huge factor that the person doing the ultrasound needs to know about vasa previa and who needs to be screened for it.

Dr. Rebarber: Yeah, and I mean, again, the key is also just getting it right as far as the diagnosis too, because you can scare people. In the differential diagnosis there are, what we call false positives because there are vessels in that area. There could be maternal vessels, what we call cervical uterine vessels, so they’re not vas previa, they’re not a fetal vessel.

One of the ways to differentiate those two is something…using called pulsed wave doppler, and doppler actually will look at and measure a rate of which the blood is flowing. And often, if you get a fetal heart rate, particularly in a fetal artery, that is heart mnemonic or diagnostic because the fetal heart rate is much more rapid than the mother’s heart rate. So that’s one way you can differentiate it from maternal vessels.

The other is you can get what’s called a cord presentation. So the umbilical cord could be near the opening of the cervix within the sac but not on the membrane that often moves. So there are things that can create false positive results and actually scare people when this is not the diagnosis. So if there’s suspicion of it but it’s a place that isn’t exactly sure, it doesn’t often pick it up, sending it to a tertiary care center that has a lot more experience with this is important to rule this out and create a management plan that optimizes outcome.

But there are false positives as well with ultrasound as with every technology. And MRI doesn’t really add anything to the diagnostic value of this particular condition, though there are some doctors that send for that, but that’s generally not something that is really that helpful.

Dr. Fox: Yeah, I mean, when we’re looking for it either to screen for it or someone has it or to map it out and to see how it’s progressing, you know, we’re generally gonna do vaginal ultrasound, transvaginal ultrasound because you can really see that area that, what you call the internal cervical loss, which is basically the opening of the cervix on the inside, meaning from the inside of the uterus towards the cervix, the most inner portion of the cervix and see, is there a blood vessel there or close to there or not.

We have the ability to sort of use color flow so we can map out vessels and then we can sort of see what direction the blood’s going. And then we also have the ability to do 3D imaging to really map it all out and see, you know, is this going left, is it going right, is it, you know, going left and then hooking upwards because you can’t always do that in your traditional two-dimensional imaging and really get a sense and map it out. Because like you said, it doesn’t even always have to be covering the cervix as long as it’s near the cervix.

And different people define what does near mean. We usually do it within two centimeters. Some people have a sort of a wider target zone around the cervix, but it’s advanced ultrasound. It’s actually pretty simple if you know how to do it, but not everyone knows how to do it because it’s not something that people do every day, vaginal ultrasound with color and 3D, and all this stuff. So going somewhere that does a lot of this is important.

And again, as the patient, how would you know if you need this, you know, if you have a twin pregnancy, if you used to have a placenta previa, you know, longer have a placenta previa, if someone told you you have a bilobed or two lobes to your placenta or maybe someone told you that you had this term velamentous cord insertion, maybe ask and say, “Hey, did you check if a vasa previa or not?” And if they say, “Oh, yeah, we checked, we did A, B, C, D,” it’s probably fine. If they said, “Huh, what’s that?” You may want get a referral to somewhere else.

Dr. Rebarber: Right. And actually, and just recently, the American Institute of Ultrasound and Medicine combined with the Society of Maternal Fetal Medicine, American Logic [SP] Society, they all put up sort of part of this statement on standardizing ultrasound and looking at the, in the mid trimester, 18-to-22-week ultrasound examination… This is now about seven, eight years old.

But they suggested in the document that the evaluation of the placental appearance location, site of the code insertion is part of this examination and ruling out vasa previa in the setting of a placenta previa in the mid trimester should be part of the standard evaluation. Which is great because we sort of have been advocates of screening for this, and certainly at least based on risk factors routinely given the catastrophic nature of it.

One of the first people that sort of pioneered a lot of this work is a guy by the name of Yinka Oyelese who’s actually up at Harvard. And we worked together for a lot of years on a lot of these cases. But he had worked with the Vasa Previa Foundation and put a whole series together and sort of brought to light a lot of this often-missed and fairly easily diagnostic event, but again, it often was not looked at and often missed. And so, finally about six, seven years ago, they needed standard that this should be looked at and it’s part of a standard scan.

Dr. Fox: So if we’re doing this and we diagnose it, right, we say you have a vasa previa, strong looks like a vasa previa, what do we do at that point?

Dr. Rebarber: So I always tell people this the best thing that can happen to you, and they kind of are shocked. And I tell them, “Well, whoever was gonna be was gonna be, but the fact that we diagnosed it tells us that we basically have really good management strategies now that can help to give over 99% out good outcome and fetal survival with good prenatal care and early delivery.”

So we tend to, somewhere between 32, 34 weeks, admit people to the hospital and then give them steroids to help the lung mature and then deliver somewhere between 35 to 37 weeks when we make this diagnosis. So doing an early delivery by C-section prior to the onset of labor, even though you’re delivering a preterm infant, and has a significantly improved survival. So that’s what most people are doing.

Again, this is not what we call evidence-based, you know, randomized controlled trials on this. Most of this is through retrospective data, but that seems to be what most people feel is probably reasonable in something so rare because we’re never gonna be able to do randomized studies to identify what’s the best type of treatment for this population.

The other issue is there’s also a lot of disagreement on actually the diagnosis when it’s not sitting exactly on the cervix but near the cervix where you see a fetal vessel. In our series and our publications, we used any fetal vessel that’s within two centimeters of the internal opening. Some series and centers advocate any fetal vessel that’s within five centimeters of that.

And so to recommend this management and delivery. So there is some variability on the diagnosis, how close is too close, and there is some ranges of when people will deliver patients and how early probably because of the fact that some are sitting exactly over the cervix, some are near the cervix, so some doctors might wanna give the baby a little more time for development. So that’s why I gave some ranges. But early delivery is the key.

Dr. Fox: Yeah, I mean, everyone’s gonna recommend two things, a cesarean instead of a vaginal birth, and delivering early before labor. And how to do that exactly, usually it’s gonna fall somewhere between 34 and 37 weeks, potentially earlier if, you know, there’s preterm labor or twins or, you know, others sort of risk factors of delivering early. But I’d say most, it’s gonna be somewhere in that 34 to 37-week range. And again, the exact, you know, where that’s gonna land depends on a lot of variables, but expect it to be preterm. Under 37 weeks is preterm, and it’s gonna be a cesarean.

And that strategy, which is, again, different from center to center, different from hospital to hospital, different from patient to patient, even, like in our practice, we individualize it to the exact timing, but they seem to work. And then what about… So that’s what we do at the end of pregnancy. So let’s say we’re diagnosing this at 20 weeks of pregnancy, give or take, and we’re talking about delivery at somewhere 34 to 37 weeks. What do we do between 20 weeks and 34 weeks? Is it routine prenatal care, or is there some sort of enhanced prenatal care or more cautious prenatal care? Like, what do we do differently if someone has this diagnosis?

Dr. Rebarber: The recommendation if they have a diagnosis by SMFM is to come back somewhere between 28 to 32 weeks to get another ultrasound once you diagnose it at 20 weeks, and basically that’s it. And then plan delivery afterwards. We are a little more cautious in our group, and we’ve actually seen patients serially every two to three weeks to measure the length of their cervix as a predictor of risk in preterm birth. We’ve actually, in some cases, have also added fetal fibronectin testing to predict the likelihood of preterm birth and just to be super cautious with our patients partially because some of our patients travel from long distances and are far away, and we’re trying to identify who’s at greatest risk that might need earlier hospitalization.

And so we’ve done a lot more serial surveillance and monitoring. We check growth at intervals four to six weeks. And then usually, we’ve admitted them around 34 weeks, delivered around 35 to 36 weeks. Some patients, we’ve admitted as early as 32, depending on the distance they have to travel, the length of their cervix, their obstetrical history. So you’re sort of trying to individualize admission based on various other risk factors for a preterm birth.

With multiple gestations, we are even more aggressive as far as monitoring and admission, and so we tend to monitor these patients, probably admit them around 32 and deliver around 33, 34 weeks with vasa previa.

Dr. Fox: Right. That’s just because twins are more likely to go into labor early than a single child.

Dr. Rebarber: Right, exactly.

Dr. Fox: And then one of the interesting things that I know that you have described in our series is this idea that if you have it at 20 weeks, it does not mean necessarily that you’re gonna have it at 34 weeks. Meaning there is a potential that this can resolve sort of like a placenta previa, that if you have it at 20 weeks, it does not mean you’re gonna have it at 37 weeks. And this was, I don’t think it was a new concept, but it really hadn’t been broadly described. So talk about that a little, like what you found in our series of patients.

Dr. Rebarber: Well, actually, it was a relatively new concept and we sort of quantified it in our series. There were actually series on vasa previa reporting one or two cases of isolated, sort of resolution of vasa previa that the vessels seemed to move out of the way. They didn’t really much focus in these prior publications, and there are really only two that mentioned this event or this concept. And so we wanted to look, at because we kept seeing as we were prospectively identifying a lot of these cases somewhere between 16 to 20 weeks because we tend to do earlier ultrasounds, that they would, a lot of times, resolve.

Now, that happens with placenta previa too. And one of the mechanisms of how a placenta previa moves essentially off the cervix in a way. And there’s some landmark papers that were published several decades ago looking at the rate of migration over time for placenta previa is thought to be two ways.

One, the placenta has what’s called differential growth. It grows the more at the top than at the bottom and the bottom part dissolves essentially. And so the placenta is sort of an active organ that cell replication. And so it tends to have what’s called differential growth towards where the top is because there’s more oxygen at the top of the uterus than at the lower part.

And additionally, as the uterus stretches and grows, the lower part of the uterus, what we call the lower uterine segment, stretches out, and that stretch of the wall of the uterus itself allows whatever’s implanted in one place to give an impression of it migrating upwards. So you have this muscle stretching and migration of the placenta. In the vasa previa, the vessel itself is not physically moving, but the muscle in the lower segment stretches. And so as the uterus grows, particularly in the third trimester, that lower uterine segment stretch gives the impression of migration of this vessel.

And we looked at probably over 100 cases of vasa previa in our series. And this was actually Dr. Clara who was a medical student at the time, put the beta set together, if you remember Katie. [SP]

Dr. Fox: Of course. Do I remember?

Dr. Rebarber: Basically, it was…

Dr. Fox: I spoke to her last week.

Dr. Rebarber: Oh, great. So amazing. She put this beta set together, was presented at a national meeting, and then published in American Journal of Obstetrics and Gynecology in 2019. And it really was the first series to quantify sort of resolution. And what we showed is that the earlier you identified it, the more likely it’s to resolve. And our resolution was if it passed over two centimeters away from the opening. And additionally, in those, what the rate was, it was about 39% where you had this sort of resolution of it.

And it was a neat paper that we put together that she worked really hard on and it quantified the resolution and also by gestational age. So after about 28 weeks, if you had a vasa previa, the likelihood resolution was exceptionally low, particularly if you were over the cervix, it was almost zero. Whereas, if you diagnosed it at 16 weeks, the resolution rate was quite high in the 60% range, particularly those that were near it but not on it.

And so, again, I think, you know, if anybody wants to look that paper up, we do have a nice graph looking at resolution by distance and time at gestational diagnosis. So I think it was a novel concept to some extent, but certainly, it was novel and medic. It provided people some kind of statistical counseling to be able to give people as to when that would resolve.

And a lot of those patients that resolved, over 50% of them ended up with vaginal deliveries and did require C-Section, which was also reassuring to us that we felt were using the right number as far as two centimeters. And we think five centimeters, within five centimeters, internal opening is actually pretty aggressive and you’d end up doing a lot of C-Sections. So those patients who did have resolution, over 50% accomplished vaginal delivery safely with no increased risk of bleeding from those vessels. And so that was reassuring from that trial as well.

Dr. Fox: Yeah, and I’ve found that over the years, either because of that study or just coincidentally, we’ve been getting more and more referrals for people who were diagnosed with vasa previa somewhere else to either double-check, you know, like a second opinion or just for counseling about it, or even for full, you know, management of pregnancy and delivery.

The management of pregnancy delivery is not particularly complicated. If you know it’s there, you know, all OBGYNs can do a C-Section, you know, 34 to 37 weeks. They just have to know that, you know, someone has to tell them someone has this to do it. But I find it’s really interesting because some people they come and we feel like they’ve been misdiagnosed in either direction, either they were told they don’t have it, and we find out they do, which is pretty terrifying, actually. Or they were told they do have it and we find out they don’t either because it migrated from the time it was diagnosed to us or just because we maybe have a different way of diagnosing it.

And that’s why it’s, you know, it’s also…it’s an option to get a second opinion if you’ve been given this diagnosis or you’re not sure if you have it. Because, again, the person doing the ultrasound should be able to like literally point down the screen and say there’s the cervix, there’s the blood vessel, and here’s a ruler. And just there, you could see how close it is. This is not, you know, if you get the right picture, it is clear as day when the blood vessel is near the cervix. You literally can just measure it.

Dr. Rebarber: Yeah. I mean, but it can be quite challenging to differentiate maternal versus fetal vessels. It can be difficult because the fetal head becomes well applied to the cervix and it makes the vessel disappear. So you always have to make sure when you are looking for this, the fetal head is pushed upwards so that you have a clear view of that lower segment.

3D ultrasound really makes it clear to patients. When I put the 3D ultrasound that, you know, my sonographers always get upset when I walk in because they know I’m gonna be there about 15 minutes, you know, playing with the 3D. But, you know, when you create a 3D image for the patient of the lower segment and you show them the vessel, you show the opening, I think it crystallizes the vessel itself and you can really see that and you can differentiate those from maternal vessels or artifacts that can be created.

So, yeah, I mean, I think, you know, good diagnosis is really important. Measuring and distance becomes relevant to planning delivery and/or, hopefully, avoiding a C-Section if it’s migrated out of the way. And I think that’s also the message, that once you diagnose it, let’s say at 20 weeks, you can be quite optimistic, and oftentimes, particularly ones that are not on the internal opening of the cervix, but near it, that those likely will move out of the way in the majority of cases, so.

And that’s what we tried to show with our data. And I think that’s really important, to serially watch it, serially monitor it, and you can see that migration and you can reassure people that it is moving out of the way and that it becomes less of a risk. And I think that’s reassuring to people.

Dr. Fox: Amazing. Andrei, thanks for coming on to talk about vasa previa. I know it’s one of your many passions, but this is on that list.

Dr. Rebarber: It was one of my interests dating back to many years ago when we had a patient who I actually had not scanned, but we had taken care of and she had an ultrasound. This was back in the ’90s and it turned out she went into labor and we did not diagnose the vasa previa. And so it wass very unfortunate, sad event. And that can be avoided if you are looking for it and focus on risk factors.

Dr. Fox: Awesome. All right, well, thank you very much, and I’m sure we’ll have you back on the podcast, and I’ll probably speak to you about nine more times in the next few hours.

Dr. Rebarber: Yeah, great. Thanks.


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