Hello and thank you for coming to listen to my talk about the evaluation of the high-risk pregnant mare with ultrasound. I wanna thank the organisers of this meeting for inviting me to give this presentation. And I also wanna add that if you have any questions about anything that I've discussed, feel free to contact me at my email at new Bolton centre, which is vreef at vet.upenn.edu.
And you can easily find it on the Pen's website. So, we got involved many years ago in looking at the high risk pregnant mare and trying to figure out if we could come up with a way in late gestation. To detect foetal stress and hopefully ultimately intervene and improve the outcome.
And so at that time, we were looking at some of the data that was out there in the human literature, in particular looking at the human biophysical profile. So, That ultrasound pictures of a human foetus, and ultrasound is used in late gestation. We know it's used in many stages of gestation, but it's used in the high risk pregnant, excuse me, human, woman to look for evidence of foetal stress and in humans, they've identified.
A number of different structures or abnormalities that are related to foetal hypoxia, acute or chronic. So, with acute foetal hypoxia in the human foetus, the first thing that's noticed is decrease or absent breathing movements in late gestation, and breathing movements are present. In the human foetus in late gestation normally.
And then they notice that the reactivity, the heart rate, so the heart rate range is decreased or absent. And as the hypoxia increases, there may be fewer gross body movements or none altogether, and then the foetus may lose tone. And in the human with chronic foetal hypoxia, there's a decreased amniotic fluid death.
So obviously there's a difference in the human placenation and the equine placenation which is diffused. So we had to think about other things that we could also include, but our high risk bear population, this is primarily what it consists of, and usually it's a mare that's, you know, bagging up too soon, she's too large. Or she's had a history of some problem that might impact her ability to successfully deliver a fall.
In the end, we had a number of parameters that we looked at in our initial research, but we ended up with in a multivariate analysis, these seven parameters that actually were associated with outcome in the foetus. And initially we went and described normals. .
More recently, this paper, has come out where they took, 3 of those parameters, foetal aortic diameter, foetal heart rate, and the combined thickness of the uterine placental unit. And called this a rapid equine pregnancy evaluation, sonographic evaluation, and looked at how well that correlated in their patient population with outcome and compared it to our evaluation, and you can see that they're pretty similar. So what's involved?
We, we clipped the ventral abdomen of the mare from basically syphoid to utter, . If we happen to be something in earlier in gestation, we may not clip them quite as far. But most bears ventral abdomens haven't been washed or cleaned in a long time.
And you usually really need to clean them well and clip them to get good images. And then we apply copious amounts of ultrasound gel. And the foetus is usually sitting in late gestation in a position somewhat like this.
And so if you think about the mare's umbilicus and you look at that V-shaped or fan-shaped ultrasound image plane from a a curved linear transducer, the fetus's heart is actually usually located somewhere near the mare's umbilicus. So that's a good place to start, and you wanna start with a large curvilinear transducer. So you're talking about a, usually a 3 megahertz linear transducer that has some range of frequencies and ideally you'd like to have a depth of display up to 30, excuse me, 30 centimetres or more if possible.
And then you want a higher frequency probe that you can use to evaluate the utero placental unit. And sometimes you can actually use a tendant probe, but often you need to use something like a microconvex or medium convex transducer just depending on how much ventral edoema the mayor might have at that time or how good your image quality actually is. And the other thing is, I think it's much easier to scan.
And get oriented, figure out like foetal orientation and things by scanning parallel to the mare's long axis. So that way it's easy to figure out foetal orientation. You can figure out foetal numbers, .
We can evaluate by looking at the rib cage and the the thoracic region, breathing activity. We can calculate a heart rate. You don't have to actually sit here and look at that with your watch and or have somebody give you 15 seconds.
You can use the M mode capability in your machine to actually calculate heart rate for you and evaluate rhythm. And then we wanna look at the diameter of the aorta, and the thoracic diameter, cause that gives us a really good idea of foetal size and whether your foetus is, this mature for its gestational age or you might have intrauterine growth retardation. We want to look for the foetal horn because if it's present, it's really unlikely that there's twins in this mare.
I don't know of anybody who has identified a foetal horn in a twin pregnancy. We look at the quality of the foetal fluids. We look at the contact between the uterus and the placenta, measure the amount of fluids that's there, and of course, measure the combined thickness of the ute placental unit which is CTUP.
You need to be careful not to measure the vena cava as the thoracic diameter. So if you look in this video loop, we've got a large vessel coming in up here into the right atrium into the right ventricle. So this is a vena cava, which is actually quite large.
The aorta comes out of the centre of the heart, and although we don't quite see the this is the aorta here, although we don't quite see the aortic valve. So, this is, this is the structure in the centre that you wanna measure, not the vena cava. So, non-fetal horn, as I said, identifying that is important and making sure that there's no twin pregnancy.
So on the bottom left, you can see a cross section of the foetal horn. There's a lot of folding of the whole uterus and Coriolanos, so it can be quite thick. And so we don't measure the uteroplantal unit in that region.
. We measure the utero placental unit elsewhere and if we can get a high quality like tendon probe like you can see on the right, we can actually measure the uterus and the corriolantos. And you can see this mirror has, as most do, there's lots of vessels in the uterus that you can visualise here. This is the, hippome that's squirting through the allantoic fluid there next to the foetus, and you can even see a little baby hippome right there on that side, and that's normal.
So those are normal. Then we're gonna look at heart rate and rhythm. So you don't need to get any particular view of the foetal heart.
You just wanna get in the very cranial thorax, so you can see how the thorax narrows down to this little triangle. And then we're gonna put an M mode cursor through anything that we can see that looks like it's beating. And then we're gonna put the cursors.
On two of those identical structures and the machine will calculate heart rate for you. And so if you follow heart rate through gestation, it gradually gets slower and slower. And you can see there, those are in our normal population.
Those are our normal foetal heart rates for mares that are over 330 days or equal to or less than 330 days. So you can see the heart rate slows and and on ultrasound, we would see an average mean heart rate range of about 15 beats per minute. StephanieBuca did a longitudinal study following a number of mares from mid early mid gestation on, and you can see there that the foetal heart rate consistently decreases over time as the fall gets closer and closer to term with a similar foetal heart rate at term of about 66 beats per minute.
So that's what you should see normally. The aorta, as I said before, you can recognise because it comes out of the centre of the heart. So on the bottom right loop, you can actually see the aortic valve right there.
And we actually wanna measure the ascending aorta right above the sinus of El Salva. At least that's where our normal measurements were taken, as you can see on the bottom left there. We measured from the near side of the aorta to the near side of the other wall of the aorta.
And it correlated with maternal prepartum weight and with the weight of the full. So it's a good way to get an idea of how How large the full is with an average of about 2.5 centimetres as you get to term.
And so on the bottom left, you can see another a measurement of the aorta and on the up, excuse me, bottom right, and on the upper right, that's the vena cava coming through and branching through the liver. So that's the structure that you don't want to measure that called a vena cava. We measure across the thorax of the fall using the diaphragm as sort of a central point and we're measuring from skin to skin.
At the level of the diaphragm and just roughly this thoracic diameter should be about 10 times the, the aortic diameter. So that's a nice way to kind of check yourself to make sure that you're measuring the right structure. If there's a lot of discrepancy in those measurements, you may wanna go back and try to get another aortic diameter or reevaluate your thoracic diameter.
Keep in mind, like, ideally, we want a, a, a withers to girth measurement of the thoracic diameter, not a side to side, but oftentimes, you know, we can't get the fall to be in the exact position that we want. Here, we're looking for breathing movements, looking for the movement of the ribs, relative to the diaphragm. So that fluid-filled structure that you're seeing is actually the stomach, so that's fluid in the stomach and the lungs are on the far left.
And the diaphragm is also on the far left, so the diaphragm is like right there, and this is long, and this is liver here. So it should be there in the normal foetus in late gestation. This is much earlier in gestation, but I put it in there because the foetus is like moving all over the place.
So, most foetuses, if they're moving, they have tone. So tone means a loss of tone means you got a flaccid lymph foetus. And then we evaluate the foetal movement like throughout the whole time that we've done the scan.
So we don't make an assessment of that. Until after the scan has been completed. And then we're gonna look for the maximal vertical depth of the allantoic and amniotic fluid.
So that's an example of how we measure it. One is the allantoic fluid, and two is the amniotic fluid. And usually the biggest pocket of amniotic fluid is in the foetal axilla, so it's usually near or in front of the stifle area on one side or the other.
And so you can have too much or too little, amniotic or allantoic fluid and so you can see It's abnormal. Those are abnormal measurements, which are two standard deviations from the mean of, the amount of fluid that should be present. In the early gestation, if you see a lot of particles in the amniotic or atoic fluid, it's abnormal and that has been associated with a poor outcome.
But in light gestation, we could not, although we graded the particles, find any association between this and outcome and there's a lot of particles that get stirred up with just foetal movement or transport of the mare. So this combined measurement of the uteop placental thickness. You can see here from Matt Stradson's work was relatively unchanged in his control mares, from 150 to 270 days of gestation.
And then it starts to increase, and I always think of it as like the normal, like the month of gestation plus one would be like the normal fitness of the uteroplantal unit. So in this study, he did find a few mares that had a significant thickening of the combined utop placental unit that had placenitis and they were treated. So this is an example of how transabdominally you can measure the combined thickness of the uteer placental unit.
You wanna look for areas where the foetus is not lying on the uterus, so that there's actually allanttoic fluid between the foetus and the uteroplantal unit. Because, you'll get an abnormally, you know, it'll be a smaller measurement with the weight of the foetus on the uterus than if that's not present. So we take multiple measurements, you know, looking all around for where the thickest and thinnest, measurements are, but we don't measure in the non-fetal horn.
So these are just some more examples of measuring the, CUPT and you can see that. And this horse, this is all one horse, it varied from 5.4 millimetres to 9 millimetres depending on which portion of the uterus, we were evaluating.
Those are all normal. You can see vessels and so we don't wanna mistake, vessels as areas of separation between the uterus and the placenta, but we did see small anechoic areas of separation in our normal study in just 10% of normal mares. But most of the time you're just looking at blood vessels there.
So we found that our initial studies, 6 variables that were related to outcome, and you can see that if you had an abnormal foetal aortic diameter, those were too small, decreased foetal activity, increased utop placental thickness, or areas of utop placental separation, 100% of mares with that abnormal variable delivered an abnormal fall. And you could see with the heart rate and allantoic fluid depth, it was 75% of mares that delivered an abnormal fall. So, Then we looked at this prospectively.
These are data from the prospective study where we looked to see what the outcome was, if that variable was abnormal. So you can see the ones that had heart rate abnormalities in our study weren't that many, only 5, and 3 had rates that were too high, so you can see the outcomes of them. One was just a full that was born to who was really tachycardic and had a large colon torsion, but it was actually a normal full.
One had a heart rate that was too small, I mean, too low. It was a, this mature full and one full had a lack of heart rate variability. It was an abortion.
So, This is our, our, our data basically as far as what the definition, when we look prospectively at the next group of more than 70 high-risk pregnant mares. And you can see we had a number of late gestation mares, some mares that didn't fall until after 360 days, and the full's heart rate, Got quite low. And if it was below 41 beats per minute, then it was significantly associated with an abnormal outcome.
You can see the full on the bottom right, Has an M mode echocardiogram, and we're just doing an M mode through any part that we can see it happened to be the aortic valve, but you can see that the rhythm is not regular. And so the arrow is pointing to areas where there's significant irregularity in that fetus's heart rhythm. That is the same foetus that you see on the left, and that foetus did, did not survive.
When the foetus dies, they usually sort of curl up on themselves and there's not very much fluid surrounding the foetus anymore. And oftentimes they will, get gas, within the foetus, so they become emphysematous, and so, sometimes it's hard to recognise much like here you can see bones which have to be some part of the vertebral column. Difficult to identify exactly where that is.
You're thinking it's probably thorax because it looks like there's a limb here, but you don't, it looks like maybe it's a little pointy here, but you don't see it very well. Here you see lots of gas here present in this foetus and gas in the foetal fluids. So emphysematous foetus.
So that's foetal death, so obviously no heartbeat. And you can see here if we had, we looked at breathing prospectively, and in 4 of our foetuses, we saw no breathing movements and 2 that were irregular, and you can see that 5 of those 6 fos had peripparture and asphyxia syndrome or were dummy fos, and 2 of them didn't didn't survive. I think the aortic diameter, just as in that rapid test is, is really valuable to get comfortable measuring the diameter of the aorta because then you can identify these folds that are small for their gestational age and you can see that Again, a lot of these falls had peripparture and asphyxia syndrome or dummy falls and were dismature or premature, and this the high number of those falls actually did not survive.
So that's an important finding that you can relate to the owner, sort of getting them prepared for the fact that there may be an an adverse outcome. Again, if the foetus isn't active, you can again see that Again, the likelihood that they may be a dummy fool is high, and, . Another thing that you can report to the owner.
Mares that are excessively large for their gestational age may have hydrops or twins. So this is a mare with hydrops amnio, and she had an excessive amount of amniotic fluid, which ultimately we define as greater than 18.5 centimetres, which is 3 standard deviations from the normal mean.
. And many of them have com combination of hydrops, amn and hydrops allantois. We also saw horses that had a decreased amount of allantoic fluid, and those fos were again, the majority of them had peripparture asphyxia syndrome, and half of those fos actually did not survive. And in humans, a decreased amount of foetal fluids is associated with chronic intrauterine hypoxia.
And then what about thickening of the utero placental unit or that combined CUPT measurement. So, that's, that's something where you can actually intervene, right? And start, treating the ma for placenitis.
And so, here you see a wide variety of, different measurements for the combined thickness of the uteer placental unit, from 2.1 to 2.6.
And the one on the top, I obviously cut off the measurement. But it's more than 22 centimetres. You could see the centimetre markers on the side.
And that ribbon candy, the upper picture to me looks like the old fashioned ribbon candy. That's an abnormal appearance to see in the corriolantos, and it's usually associated with significant placenitis and or some placental edoema. The increased ecogenicity that you see in the bottom right image.
Between the two hypochoic layers, is of concern, and so you need to look critically at one like this to see is there fluid dissecting between these two layers. So this is uterus, and this is corolantos, and is this, dissection associated with utero placental separation and what's separating it is purulent material. So, you can see here if there was an abnormally thick CUPT that almost all the falls were abnormal, but we started treating those mares for placenitis based on finding that sick thickened uteroplantal unit.
And so the survival rate of that, those falls, even though they were abnormal at birth, was much higher because we could actually intervene and do something about it. We also had some that were abnormally thin, and all these placentas were evaluated histopathologically, and those that were abnormally thin did have fibrosis and hypoplasia detected in those thin areas. And those folds.
Had, you know, peripparture asphyxia syndrome or were dummy folds. And then again, if we had large areas of utop placental separation, big concern, almost all those folds were dummy folds and were abnormal. So here's some examples of uteroplantal separation where you can see the arrows pointing to this hypochoic area between the uterus and The Coriolanos.
And so, This is uterus right here. This is the area separation, and this is corolanos and allantoic fluid. Just wanna mention cause sometimes it's if you haven't done a lot of these, You might get confused by this large like heterochoic layer, and that's the retroperitoneal fat layer of the mare.
So the uterus is right next to it, as you can see here unless you can clearly see like the peritoneal reflection. So of those falls that had uteroplantal disruption, you can, this is just gives you a little more information about them, but the survival rate was impressively high really for having areas of utop placental, disruption. The cardioformplacentitis is one form of plaitis that's been identified as, as being associated with fluid dissecting between the uterus and the lanokoran in the cranial uterine body.
And this is an example of one horse with the cardioform placenitis, and you can see this ecogenic swirly fluid. Here. So the uterus is very thin.
It's right here. You can see all this turbid fluid between the uterus and the Coriolanos, which is out here. And then this is allantoic fluid.
In this case, this is the foetus that's quite close. So a large amount of, dissection, souteer placental separation occurring in that cranial uterine body with the cardioformplanitis. And you can see the combined thickness of the uterus and the lanokoron here was 4.1 centimetres.
So really large, impressive, thickening. So, other findings associated with the foetus, so. Here's some foetal scans.
We do try to get an exercising heart rate too. We identify like what the gestational ages of the foetus. Like this foetus is on the upper left is 294 days of gestation.
We identify whether they're sedated or not cause that certainly will slow foetal heart rate. You can see in the upper, excuse me, right, we're measuring the aortic diameter. So we've got 1.9 centimetre aortic diameter, but this is a foetus that's just under 300 days of gestation.
And then we're measuring the thoracic diameter right underneath. So that's almost 19 centimetres. So that kind of matches, remember I said that the thoracic diameter is usually about 10 times the fetus's aortic diameter.
So those things fit. And then we're looking at foetal heart rate. Here and we've got a range of foetal heart rates from 89 to 96.
We usually like to see a heart rate difference of at least 15 beats per minute. And this is the full of the cardioformplanitis. So you can see all this echoic fluid that's dissecting between the uterus and the lanokorion.
So there's less heart rate variability than we would expect. This fall was delivered a month after the scan was obtained and it was a dummy full, but it did survive. This, mayor came in for, Early lactation and significant other development, and this is the scan at the time that she presented, and you can see there's this Incredible hyperchoic, almost sparkly appearance, .
Between the uterus and the Coriolanus, you can see it here on the rectal scan, where we've got this marked, again, sparkly. There's foetus, sparkly material between the uterus and the foetus. You can even see it a bit.
It's a thinner layer right here, when we're looking at the foetal heart and getting a foetal heart rate. This marrow was at 300 days of 301 days of gestation. The fetus's heart rate is 59 beats per minute, which is slower.
Then it should be for that stage of gestation. So indications of foetal stress, there's clearly dissection of purulent material that goes from at least the left mid abdomen all the way back to the cervical star region, and the fall was actually delivered that night. And this is the appearance of the placenta.
And you could pick that material up and it was just this very thick, stringy, they described it more like thick peanut butter, material that was dissecting between the uterus and the lanokorion, severe, bacterial and fungal placenitis, so strep, E. Coli and aspergillus were all identified, in that material. If the foetus was malpositioned, They all needed assistance, and by malposition, we just mean that normally at late gestation, the fetus's head should be up near somewhere near the cervix or in the more dorsal portion of the abdomen, not down on the ventral abdo abdominal floor near the stifle.
So when you see the foetal eye and it's in a late gestation there, Just be aware that perhaps the foetus is not quite in the right position for delivery, and all three of those foetuses in this prospective study required some assistance at the time of delivery. So when we made our biophysical profile, this is the complete biophysical profile. We gave it 2 points if it was normal, and as I said, 0 is abnormal.
And so if 2 parameters were abnormal out of those 7, all the foetuses were abnormal, so, wanna consider some sort of intervention that just might be starting the mare on antimicrobials if she's not ready for parturition. And if, one thing is abnormal, it's likely that there still could be an abnormal foetus. You could have a perfect, score and still have an abnormal foetus if you have dystosia at the time of parturition.
But it is useful to intervene and decide like what. Kind of things you might wanna do. If there's placental abnormalities, which are the things that we can definitely treat prior to parturition.
There may be indications where the clinician feels it's time to induce the fall or less likely do a C-section. And so that's how it could be utilised. And then we can also use it, earlier in gestation to identify twins.
And so it, you'd think this would be quite easy, but it actually sometimes can be somewhat challenging in that it's hard to be sure that you're not imaging the same foetus. So sometimes it's quite clear, like one foetus is an anterior presentation and one foetus is in posterior presentation, or like in this case here at 273 days, you can see that a heartbeat. In the left foetus, And on the right, bottom right, you see no heartbeat.
And so confirming that there are no, there's no heartbeats is maybe a little more challenging that you think cause you wanna be sure. That, you know, you, you make decisions based on the fact that one foetus or sometimes two foetuses are actually both dead. The other thing, so there may be different sizes of the foetus.
So sometimes both foetuses have the same aortic diameters and the same thoracic diameters and similar heart rates, but sometimes there's one that's clearly smaller than the other, so that's helpful. And then the other thing is you want to look for two placentas that are side by side, as you see here, and so there's one foetus on the left. The placenta or uter placenta unit where's is actually coming down here like this.
So there's a foetus over here with allantoic fluid. And there's a foetus over here with basically no fluid around it. And that's typical after a foetus dies.
It tends to curl up in the foetal position and the foetal fluids get resorbed, so often you don't see many. Fluids around the foetus. And so sometimes identifying a dead or mummified foetus is a bit challenging cause there's no fluid around it, and it's hard if there's a lot of decomposition of the foetus.
Sometimes to identify structures, but you can always usually see the little triangle of the foetal thorax and identify that as in this case here where this foetus is dead. So, here we have twins, Even later in gestation, right? So this is the marrow is abnormally large, but she's near the time when she should normally deliver a fall.
You could see that we have two foetal thoracic diameters that are just over 19 centimetres, so that would indicate that the fall is gonna be smaller than your typical term full, and we have one aortic diameter, . The one of the right caudal foetus of 1.84, so close again to 19 centimetres.
So again telling you that the foetuses are probably gonna be small. And here's their foetal heart rates, and so you can see that one has a heart rate of 71 and one has this heart rate of 73 beats per minute. So these foetuses are pretty similar in terms of size, aortic diameter, heart rate diameter, excuse me, heart rate.
And this mare delivered two healthy foals that were smaller than normal, which is typical for twins, and they were both a little a little bit dummy at first, but they actually did very, very well, and you can see them in the upper right corner there. And then you can also identify haemorrhage associated with the uterus and the uterine artery. So in this case, there's haemorrhage, there are two different cases where we're seeing haemorrhage into the antokorion, between the antokorion and the uterus.
So this is uterus here. We've got anechoic and hypoechoic fluid between those two structures. Similarly the same thing occurring over here.
So you can identify what you think is probably haemorrhage between the uterus and the lanokorion. If the mare has uterine artery haemorrhage, sometimes you'll see what you're seeing on the bottom left. Looking from ventral to dorsal, you'll see a coa swirly fluid with loops of ginum floating in it.
Or What we're seeing here, which is fluid again and dissecting into the broad ligament. Up here, and this is transabdominally into the uterine lumen. So this is paritinal fluid and haemorrhage in the uterine lumen.
But a lot of times you won't see free blood in the abdomen, because it's haemorrhaging into the broad ligament. So one thing you can do just to confirm that you probably have a significant bleed is to look at the spleen and the spleen obviously will be contracted if there's significant haemorrhage. So if you have a small contracted spleen, that kind of supports your diagnosis of uterine artery rupture.
Another thing we can see in the high risk pregnant mare in late gestation are ventral body wall hernias or prepubic tendon ruptures. And so we can actually, as we're doing in the bottom, right, we can measure the width of the hernia. If it's a ventral body wall rupture, which is usually what happens more commonly than the prepubic tendon rupture.
In this case, we have on the bottom left, both, both the full, so this is much earlier in gestation cause you can see the whole, you can see the little full thorax. And you can see here. A loop of small intestine, in the hernia, and again here you can see that the hernia gets quite close to the skin.
There's really just skin and a little bit of subcutaneous. Tissue there in the ventral abdominal wall hernia with small intestine right there. Sometimes the different layers of the hernia of the body wall will rupture and small intestine can get in between those layers, but certainly this is a ma that needs abdominal support.
With a belly bandage. As she goes through the rest of gestation with careful monitoring of that, Area. Up until the time, a partition, and she may have trouble, at parturition, because of that.
You can often see the umbilical cord when you're doing a transabdominal high-risk pregnant scan and Here in this mare, we've got the uterus plus the lanokorion. We have a large amount of allantoic fluid, and our amniotic fluid is here. Here's foetus.
And this is the umbilical cord. And so you can see tubular structures in the umbilical cord, which are the umbilical artery and vein. But you shouldn't see a fluid-filled structure which is the Eurachus, and you certainly shouldn't see.
Marked distension of one of those fluid of the eureka. So as you see here in these loops, you can see This large sort of oval fluid-filled structure. It's going down into the umbilical cord.
You can see an umbilical artery there in this loop. Over here, we put the colour on. To see where flow is, and you can see that there is flow in those umbilical vessels, but not in this anechoic fluid-filled structure, which is the Eurachus.
And then these are just two mutually perpendicular or trying to be perpendicular views of that structure, but you can see an umbilical artery, this fluid distended. Eachus, surrounding it. So that suggests that there's some umbilical cord abnormality that's causing the urachus to not be able to pass the urine through that structure, right into the adjacent cavity.
And so you need to think about some sort of umbilical artery torsion. And then the other thing is to look critically at the bladder in that fold to make sure that there's not marked distension of the bladder because the bladder can't empty normally. So you can occasionally find umbilical cord abnormalities, .
Which can be important as well. So with that, I'll, Finish this discussion about looking at the high-risk pregnant mare and how we can intervene and hope that if you have any questions, you'll reach out to me at vreef.vet.upenn.edu and hopefully you'll be able to apply this technique to your theogenology practise.
Thank you very much.