Twin-to-Twin Transfusion Syndrome (TTTS) can occur in monochorionic twin pregnancies when abnormal blood vessel connections form in their single shared placenta and allow blood to flow unevenly between the identical fetuses. Perinatologist and twin expert, Dr. Larry Rand, explains the clinical characteristics of TTTS, how it is diagnosed, the various stages of the condition and why it is so important to differentiate between those stages.
Refer to Fetal Treatment Center
today we're going to talk about monaco chorionic twin pregnancies and their complications. We said earlier that all mono chorionic twins because they share this one placenta are connected under the surface by some of their blood vessels, which allows the blood to transfuse back and forth because they're identical and they have the same blood type. This is not a problem. And as long as they send the blood back and forth evenly, there's no disease. That's what happens 90% of the time with monta chorionic twins. But 10% of the time, one twin sends blood to its co twin and doesn't get enough back. And when this happens, we have twin to twin transfusion syndrome or TTS for short, to fully understand this, we need to look a little bit more closely at the anatomy of these blood vessel connections. First, when we think of blood vessels, there are two kinds in our body arteries and veins. What makes them different is that an artery is surrounded by a layer of muscle and that allows it to pulse. The purpose of a blood vessel pulsing is so that it can send blood in a direction. Veins, on the other hand, don't have any muscular layer and they can't pulse. That's why when an artery connects to a vein, the blood will go from the artery to the vein in a uni directional channel or a one way street, we call these one way streets, arteriovenous connections or aves for short. There's another kind of connection which is an a a connection that if it exists, is really great and quite protective every now and then an artery from one fetus who meet with an artery from the other fetus because each of those arteries has a pulse and is large. These kinds of connections actually allow bi directional flow. In other words, unlike a one way street, they act more like an avenue, believing the traffic congestion. And if a pair of monte chorionic twins is lucky enough to have an A. It will serve a major protective function against forming true twin to twin transfusion syndrome. Having one doesn't make you immune from developing twin to twin transfusion, but it significantly helps. Here's what happens, especially when there's no eh eh let's say there are three A. V connections going from twin B. Two twin A. But there's only to a V connections coming back over time, Twin B is going to send more blood to twin. A twin B can get back if there were an artery to artery or a a connection here, it would help make up for this imbalance in vascular connections. But without one twin B will keep donating blood to twin A and will become anemic and have a low count of red blood cells. All of us, including fetuses, need these red blood cells in order to carry oxygen to our tissues. So you can imagine without enough red blood cells over time there can be some significant damage, especially the tissue that's very sensitive to oxygen like the brain or the heart. In this example Twin A. Is overloaded with blood that it can't send back to twin B. It acts as the recipient. The recipient twins heart has to beat all this extra blood volume around its body which puts quite a strain on it. The way we see this though is as a difference in the amount of amniotic fluid that's around each baby. So the way that we can tell that twin to twin transfusion syndrome is happening is that the donor who is anemic and is holding on to everything isn't paying enough and has very low amniotic fluid volume around it. The recipient whose overloaded is peeing like crazy and has way too much fluid around it. Ultrasound is used to be able to find how much fluid is around each baby. Using ultrasound, we look at each baby sack individually and measure the deepest pockets from front to back. In order to be diagnosed with true twin to twin transfusion syndrome. You have to meet very specific criteria. One of the twins has to have two cm or less of amniotic fluid and the other twin has to have eight cm or more of amniotic fluid. In other words, at the same time Allah go hide remedios in one and polly hydra meals in the other. The numbers two cm and eight cm are actually really important because there can be variations in what a normal amount of amniotic fluid or baby urine is at any given point in the day. So the numbers really need to be at the extremes of being low or being high at the same time. In order to be reflective of twin to twin transfusion syndrome as the underlying cause. Once you meet the criteria of having less than two and greater than eight at the same time, we have to determine what stage of T. T. T. S. You have. Stage one simply means that you meet the criteria of less than two centimeters and greater than eight centimeters. And there are no other remarkable findings if the donor twin is so anemic that it's holding on to everything and actually slowing down its urine production so much that it's bladder is no longer visible. That stage to to have Stage three T. D. T. S. We see evidence of too much strain on the recipients heart stage four Tts means that the recipient twins heart is under so much strain that it's actually developed heart failure. This is called high drops. The word high drops is actually latin for fluid retention, something that happens when the fetal heart starts to fail. Stage 5 20 twin unfortunately means that one of the fetuses has died. If you do have twin to twin transfusion syndrome, in our experience, the most important differentiating factor Is whether you are stage one disease Or if you've progressed to stage two or worse, that's because if you have stage one T. T. T. S. There's a 50% chance that the situation is going to improve on its own. It turns out that fetuses who have an a a connection seem able to balance the blood flow somewhat better and are able to correct the situation or at least keep it at bay without progressing to Stage two or beyond The other, 50% roughly, who likely don't have an a. A to protect them, will progress and have stage two or worse disease. Once you have stage two disease, there's an 80-90% chance that you will lose one or both fetuses stop and think about that for a moment. The difference between stage one and stage two is phenomenal To go from a situation where you have a 50% chance of getting better on your own to one where there is an 80-90% chance of actually losing both twins is really night and day. And that's why we make such a big deal about differentiating between stage one and stage two. Yeah.
