Genetic Jigsaw: Decoding the Differences in IVF Testing

In this eye-opening episode of "Taco Bout Fertility Tuesday," we're diving deep into the genetic pool of IVF testing. Get ready to decode the complex world of Pre-Genetic Carrier Screening, Pre-Implantation Genetic Testing (PGT), and Karyotype testing. We'll unravel how these tests intertwine yet stand apart in the IVF journey, and why knowing your genes is more than just a "find-the-disease" game. Tune in as we shed light on the intricate tapestry of reproductive genetics!

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Transcript

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When going through infertility, there are many. Times genetic testing is performed. Today we talk about the distinctions between pregenetic carrier screening, pre implantation, genetic testing. In IVF, and karyotype testing. I'm, Dr. Mark Amols, and this is taco. About fertility Tuesday. The reason I chose this topic today is because many patients, when they go. Through fertility testing, decide on whether they want to do things such as pregenetic care screening. Or sometimes when they're going through IVF, they want to do PGT pregenetic testing. But the problem is not everyone understands. These as how they look at different things. Matter of fact, many times when someone goes through IVF, they'll say, oh, I'll. Just do the PGT, and it will find any diseases in my kids. Or someone will find that their child has a disease and says, why wasn't this picked up? And that's because each test can only test certain things. And so what I want to do today is help decode the differences in this genetic testing. So that way you know what test. Needs to be done, why you didn't get a test your friend got, and why you might need a test that your friend didn't need. One thing that is definitely true is genetic testing is vital to IVF. But even if you're not doing IVF. There is always testing that be done. To help prevent things. For example, let's say you're someone who has recurrent miscarriages. You may decide to do a karyotype to find out if you carry some. Type, of genetic defect called a. Translocation, that can affect you to have miscarriages over and over. Or maybe you want to make sure there's not a disease that runs in your family, such as cystic fibrosis. So then you would do pregenetic carrier screening, where you can check if either of you have diseases and if you both have the same disease, you could. Potentially have a child with that disease. And then last, we're going to talk about pre implantation genetic testing, which is where you can test the embryos to. See if there's problems with embryos that can prevent pregnancy. But in the end, each test tests different thing. Some tests cover other tests and others do not. Let's start with the first type of genetic testing, and that's pre genetic carrier screening. According to the American College of OBGYN, everyone should really undergo some type of. Pre genetic care screening. Now, although it's recommended, you don't have to do it. As a matter of fact, most people don't when you think about it, when you're planning to have a kid, you. Say, hey, let's have a kid. And you just start trying. You don't stop in the middle of intercourse and say, hey, wait, timeout. Have we checked our genetic care screening yet? Maybe we have a disease that's passed along. Now, the reason why everyone should do. It is you could potentially prevent having a child with some disease. Now, it's not just used to, Prevent having a child with disease. Maybe you're pregnant and want to know. If your child has a problem. If both of you are tested and. You find you both have a certain. Carrier type, you could pass along these. Work through what we call mendelian genetics. So you both have to have an. Abnormal copy of the gene, and that. Would give your child a 25% chance of then having disease. Some of the most common types of care types are going to be cystic fibrosis, spinal muscular atrophy, also known as. SMA syndrome, and things like taysax disease that runs higher in certain Jewish populations. What's important is that just because you don't see this disease in your family doesn't mean you don't have it. Diseases that we see regularly in families are going to be autosomal diseases. These are diseases that it just gets passed along 50% of the time. So most people get it. But this is a recessive disease. Most people have the trait, and then you have to meet someone who has a trait. So even something as common as cyst fibrosis, which occurs in one in 25. People, when you're a caucasian, you would. Have to still meet another person with that to then have a 25% chance of having a child with it. So you can see, it would be very easy to have multiple kids and never have one kid with that disease. This is the reason why it needs to be tested to find it. Now, some people can make the argument, well, I'm not going to do anything different, I'm not going to terminate the pregnancy, or I'm not going to prevent. It, and that's fine, but maybe by. Knowing it, you know, to test for. It a little bit more late in. The future and can help maybe prevent. Your child from having some complications from it. Back in the day, when people had 810 kids, these diseases showed up more often because you had enough kids to eventually start seeing things that run in your family. But when people only have one or. Two kids, we don't see them popping, up as much. And so you can't use family history to say, oh, my genes must be good. Pregenetic care screening is testing the parents. To see if they have genes which are again codes of DNA that could. Lead to a disease state. This is very important to understand because if the parents have it, then there's. A chance the child can get it when they procreate. Now, if one of them has no. Common pregenic problems, then it really doesn't. Matter what the other partner has, because. You have to have two copies of it. Whereas with pre implantation genetic testing, PGT. That is looking at the DNA of the embryo, but it's looking at from a higher level. So imagine if we had, a lens that can look in at DNA. The care screening is looking at the actual codes of DNA and finding where. There could be problems. Then with a, wide angle lens. We come out further and now we can see the long strands of DNA and that's PGT. We don't actually see the actual DNA. Meaning like we don't actually see if the genes are there. We're just looking to find out how many copies are there, meaning how many numbers are chromosomes. And then we're looking at things like if there's places that it may be broken. So PGT is not going to find something like a cystic fibrosis or taysax. Disease or SMA syndrome. Instead it's going to find things like down syndrome because it's an extra chromosome, there'll be three chromosome, 20 ones, and then we would know that embryo has down syndrome. Just like if we saw something abnormal, where a portion of the DNA was inverted or if it was translocated. We may see that on PGT. Now, PGT can be PGTA, PGTM M, PGTSR. PGTA is where we're looking for anaploid, I mean, abnormal embryos. So that's going to be your down syndrome, Trisme 13, Trisme 18, down syndrome, Turner syndrome, all types of large DNA issues. PGTM M is when you know the. Genetic disease that you're looking for, which. Is found in the care screening, and. Then you make a probe to find that in the testing itself, it cannot find anything. It has to have a probe first. That'S created from the testing, from the care screening. And then the last type of PGT is called PGTSR. This is where looking at structural rearrangement, things like translocations, inversions and other types of problems in the DNA that aren't. As large as the, let's say, extra chromosome or missing a chromosome, but can. Then find those small things that can cause recurrent miscarriages and, other problems. So if you think of pregenetic care. Screening, it's kind of checking all the. Ingredients before we start baking a cake. We're making sure everything's there and that nothing is abnormal, whereas PGT is kind of like quality control in the embryo factory. We're just making sure now, okay, we made the embryos. We thought the ingredients are good, but. There are some issues once they were. Made, and that's because the dna of an embryo is rearranged. Sometimes when you have mom and dad, right. Not every piece of DNA you have. Is what goes into your kid. It's not a complete duplicate. It's portions of your DNA then mixed with portions of your partner's DNA, and that then makes an embryo. And there can be issues that can lead to defects in the DNA. That's why you can be normal, your partner can be normal and your embryo can be abnormal. So then that takes us to karyotype. A karyotype is when we look at the DNA, but we look at with. The wide lens where we're actually looking. At the chromosomes, but we're looking at. A little bit more detail to find even small issues with the DNA, meaning. Pieces of DNA missing or duplicated or inverted. Now, PGTA can do, and PGTSR can. Do what a, kerotype can do, but not to the same level. They can look at the large issues. But they can't see the small deletions and the small inversions. That's where a kerotype is needed. So no one should ever fall back. On a PGTA result and say, well, there must be nothing wrong because the PGTA came back normal. You would need a karyotype first to. Be able to say, okay, the dna in that parent is normal and both parents would need to have it. So the common time that someone does. Karyotype testing is if someone has recurring miscarriages. We will test both partners to determine. If either them have a structural rearrangement or something wrong. If that rearrangement is found, then that's where you do PGTSR. Now, there are many times when you. Do something like PGTA that we see some translocations and we see the multiple embryos and then we realize there must. Be a problem and then we test. Them with the care type and verify it. But the reason you can't rely on. That is because you need enough of a sample size to find it. Just because you find one embryo that might have, let's say, missing 14, but. An extra seven, and then you see. Another one that's missing seven extra 14. There's only two. You really can't make a conclusion. But if you have twelve embryos and. That'S in 60% of them, then you can conclusively say there must be a problem here. And again, you verify that with a karyotype. So the problem with using PGTA to determine karyotype things is that you don't have a large enough sample size and you have so few cells, you cannot have the detail of a karyotype, whereas. With a karyotype you have lots of. Cells because you use a blood sample. And so you can look at a much more detail at the band of each chromosome to find out if any. Of them are inverted or in the wrong location. So PGT cannot replace pregenetic carrier screening because it can only look at the. Large things, the wide angle lens, whereas. Pregenic carry screening can less know about the diseases. Karyotype is even, a wider lens looking at the whole dna, but it's also able to look in closely at smaller dna issues that may have not been seen on the PGTA. And that's because PGT uses four, maybe three cells that are then amplified to do testing on it. Whereas when you do a karyotype, you're. Using many more cells because you're using a blood sample. Which takes us to the question, how. Are each of these tests done? When it comes to carrier screening, it. Is a blood test. You can use a, bucol swab. In your mouth, but usually it's a blood test. When it comes to keratyping, the same. Thing, you can either do it with. A bucol swab or you can do it with a blood test. But when it comes to BGT, right. Now, currently the only option is to. Biopsy the embryos and test them. There are people looking at the cellular. dna inside the fluid that the. Embryo is bathing in and looking at doing it that way without even needing a biopsy. But that is not around yet. So currently, PGT testing does require a biopsy embryo. Some companies are even then testing the. Parents, like the maternal paternal, and can. Actually verify everything with the embryo biopsy. Because now they're using the maternal paternal dna and figuring out where the problems are coming from. Some clinics have found very novel ways to do this and that's actually going. To be a future episode on talk about fertility Tuesday. So for case scenarios, if you are having recurrent miscarriages, then you should do a karotype that is going to help you figure out if that's a potential. Cause for the miscarriages or if you have an unexplained loss in a late pregnancy. You would check a kerotype. In the late loss, they would check. The baby by checking the aminosynthesis for the karyotype, and for you they would. Check the blood work. Now, in the situation where, let's say. You'Ve had many miscarriages but your keratyps were normal, that's where PGTA comes into play, because now we can look for. If there's chromosomal problems after you made the baby, where in the dna, not in you, the parents, but in the. Embryo, there was a problem. PGTSR would be used if on the karyotype you found, there was a translocation. And so then we would use PGT with structural rearrangement to then look to. Find out where that problem is. So you know which embryos to put back to stop having the miscarriages. And then the last thing would be pregenetic carrier strength. That would be someone who wants to either prevent having a child with some type of disease. Or if you know that in your family there's a certain karyotype that you guys have, you might want to check your partner to make sure they don't have that. Maybe you're using donor sperm or donor eggs and that donor had that disease, then you're going to want to test you to see if you have that, because you wouldn't want to use that. Donor because you could end up having. A higher chance of having a child with that disease. Now, you could then treat that and. Say, well, listen, I'm going to do PGTM M and make a probe to prevent from having that child. But in general, you can see each. Type of genetic testing is for a different purpose. And for each purpose you need a different tool. This is why using a hammer for every repair in the house isn't a good idea. You sometimes have to use the right tool to fix certain things. Genetics are very difficult to understand because it's something we can't see. It's beyond microscopic, it's at the level of nucleic acids. And so because we can't see it, it's hard to understand. And so when we hear genetic, we assume it's just all the same. But they're not, they're all different and. They'Re four different things. And so it's very important when you. Are going through the process of fertility or doing some type of testing, talk to your doctor and find out if one test you did covers another area, and if it doesn't, you might need a different test. Hopefully I've unscrambled the genetic puzzle and. You have a better understanding of things. As always, I greatly appreciate everyone who had listened to this podcast and hopefully this was helpful for you. If ah, not, maybe it might be helpful for a friend. You can tell them about it. Or maybe it's someone in your family and now you know something a little bit more. Maybe you're going through IVF and you. Just realized, oh my goodness, we never. Did genetic care screening. Maybe we should do it. There's no wrong or right to doing it. It's just recommended. Again, no one's going to force you to do it. It's no different than PGT testing. You don't have to do it, but there are some benefits. I appreciate all the reviews everyone gives us. And again, if you like us, give us a five star review. Tell everyone about us. And again, if you have episodes that you want me to do, send me one through the email and you can send it to, TbfT for talk about fertilitytuesday@newdirectionfertility.com I look forward to talking to you guys again next week on talk about fertility Tuesday.