Why You Should Do Genetic Carrier Screening
Guest
: Louis Weckstein, MD, RE
From the Show: Reproductive Science Center of the SF Bay Area
There's been a massive explosion in knowledge surrounding genetics in recent years. Genetic carrier screening is one option for individuals planning to become pregnant, as it screens for hundreds of genetic diseases. Louis Weckstein, MD, RE, explains why this simple test is so important for detecting diseases and informing parents of potential risk.
Transcription:
Bill Klaproth (Host): So, if you could greatly reduce the risk for your child to have a bad genetic disease, would you do it? I think that answer is probably yes. So, how do you find that out? Well it’s called genetic carrier screening and here to tell us all about it is Dr. Louis Weckstein, IVF and Medical Director at Reproductive Science Center of San Francisco Bay. This is Fertile Edge, a podcast by Reproductive Science Center of San Francisco Bay. I’m Bill Klaproth.
So, Dr. Weckstein, first off, I know this topic is of importance to you. Why did you want to talk about this today?
Louis Weckstein, MD, RE (Guest): Well I felt it was really important to give our patients background on this really important topic. Because we suggest that all patients consider doing genetic carrier screening before they get pregnant. And it really takes a little discussion to understand why.
Host: Okay so, genetic carrier screening. Tell us what that is.
Dr. Weckstein: There’s a huge explosion in recent years in our knowledge about genetics. We all carry in our genes, some genetic diseases. In recent years, we’ve been able to test for more and more genetic diseases in a very cost effective manner. And there’s a couple of common categories of genetic diseases to talk about today. One is called autosomal dominant diseases. And these are genetic diseases the you will transmit to 50% of your offspring if you carry that disease. Carriers are affected by the disease, so they usually will show signs of having that disease themselves. These diseases are typically seen in your family history, so just from knowing if there’s a major disease in many family members throughout generations; you can suspect that you may carry this disease.
And examples of autosomal dominant diseases that patients have heard of include myotonic or muscular dystrophy, and Marfan’s Syndrome. A second type of disease that we want to talk about are autosomal recessive disorders. And these are often not seen in family history. Carriers of this type of disease are not usually affected by the disease themselves so, both partners need to be a carrier of the disease in order for their child to actually have the disease. There could be multiple members of your family who carry this disease but are unaware of it because their reproductive partners were not carriers of the disease, so there are no children with the disease in the family.
But if both partners carry an autosomal recessive disease, then 25% of their children will have the disease. Examples of this type of disease that people have heard of include cystic fibrosis, thalassemia, and Tay Sachs. And genetic carrier screening typically screens for these autosomal recessive diseases that people are usually not aware that they carry because there is nothing in their family.
Host: Wow. I keep thinking of that PSA you see on TV, the more you know. Wow, what a benefit that would be. A benefit and potentially scary for people too like I don’t want to know, so I don’t want to do this. So, it really presents some interesting questions. So, then why should you do screening for genetic diseases before you plan to get pregnant?
Dr. Weckstein: Since all of us carry some genetic diseases; if both you and your partner unknowingly carry the same autosomal recessive disease; then 25% of your kids will be affected by that disease. Current genetic carrier screening panels which are blood tests, can screen for hundreds of diseases and data or studies show that about one and a half to two and a half percent of couples who are of similar ethnic origin will be carriers of the same genetic disease when they are screened with one of these extended carrier disease blood panels.
If it is determined that both partners are carriers of the same genetic disease; then you can use preimplantation genetic testing the embryos with IVF treatment in order to prevent having a child with the disease. So, really great powerful knowledge to have before you do an IVF treatment.
Host: All right so you just mentioned preimplantation genetic testing again, so then why should you do genetic carrier screening if preimplantation genetic embryos routinely picks up these diseases.
Dr. Weckstein: Excellent question. The answer is that the common form of PGT or preimplantation genetic testing of embryos screens all 23 chromosomes for an abnormal number of chromosomes. Embryos in all of us should have two copies of every chromosome. An example of an abnormal number of chromosomes would be a Down Syndrome child who has three copies of chromosome 21. When we do routine IVF and preimplantation testing of embryos; we only have a very small amount of DNA genetic material that is given to the genetics lab to do the testing.
So, testing can be done for all the 23 chromosomes, but we can’t test for 250 or more diseases that can be tested in the blood genetic carrier screening panel. If we find that both partners carry the same disease with the genetic carrier screening blood panel; then we can direct the genetics laboratory to test this small amount of DNA or genetic material specifically for the disease that the couple carry.
Host: So, if a couple has a positive test for a certain disease, high probability; what happens then? Does a couple say, you know what, we are not going to have kids or how do you - what happens? Do you monitor them. I’m just curious what happens in that situation?
Dr. Weckstein: That’s an excellent question and that’s exactly why we can now do this testing so normally, if a couple knew that 25% of their kids would have a bad disease; then they would have the option to say okay, we don’t want to take that chance, we are not going to get pregnant or that we’re going to try to get pregnant on our own, accept that 25% risk and there is testing that a couple can do early on in a pregnancy, amniocentesis or chorionic villa sampling that will pick up does this pregnancy have that disease, 25% will and they would know about that ahead of time or, they can do preimplantation genetic testing of embryos and know that approximately one out of four of their embryos will carry that disease and then we just do not transfer the embryo that carries that disease.
We only transfer an embryo that does not carry the disease. So, they can reduce the chance of having a child with that abnormality or that disease from 25% down to almost zero.
Host: This is truly amazing. Amazing. So, as I mentioned earlier, for some people, maybe this is great, let’s do it and other people nah, this is scary, I don’t want to know. So, I’m just curious how common is it to have IVF patients doing PGT for genetic diseases?
Dr. Weckstein: We see a lot of patients in our practice who do not have fertility problems. They have no trouble getting pregnant. Probably one or two patients every week, but they are doing IVF with genetic testing of embryos because they already have a child who is found to have a severe genetic disease. And after they found that they had a child with that genetic disease, then they did testing themselves and were both found to be a carrier of that disease, so they knew wow we had that one out of four chance, we had that baby with a genetic disease so with no fertility problem at all; they are now doing IVF with genetic testing of embryos to prevent having another child with that disease.
And given the tragedy of having a child with severe disease that could have been prevented by having the knowledge ahead of time that both partners were carriers of that disease before they even planned for pregnancy; that’s a strong reason that we recommend patients do genetic carrier screening before pregnancy and before starting infertility treatment.
Host: So, this sounds so beneficial. It sounds like even for those couples who aren’t having a hard time getting pregnant they would benefit from this type of testing too. Is that right?
Dr. Weckstein: Correct. And it’s just blood tests that for 200 to 250 dollars you can test for 300 different genetic diseases. So, if you know heh, when my kids want to get pregnant, I’m going to tell them for sure do this testing ahead of time because if you find you’re both a carrier, you should then do IVF treatment to screen out embryos that have this disease.
Host: This has been amazing and so informative. Thank you so much Dr. Weckstein. We really appreciate it. And to get connected with Dr. Weckstein or another physician, please visit www.rscbayarea.com. And if you found this podcast helpful, please share it on your social channels and check out our entire podcast library for topics of interest to you. This is Fertile Edge by Reproductive Science Center of San Francisco Bay. I’m Bill Klaproth. Thanks for listening.
Bill Klaproth (Host): So, if you could greatly reduce the risk for your child to have a bad genetic disease, would you do it? I think that answer is probably yes. So, how do you find that out? Well it’s called genetic carrier screening and here to tell us all about it is Dr. Louis Weckstein, IVF and Medical Director at Reproductive Science Center of San Francisco Bay. This is Fertile Edge, a podcast by Reproductive Science Center of San Francisco Bay. I’m Bill Klaproth.
So, Dr. Weckstein, first off, I know this topic is of importance to you. Why did you want to talk about this today?
Louis Weckstein, MD, RE (Guest): Well I felt it was really important to give our patients background on this really important topic. Because we suggest that all patients consider doing genetic carrier screening before they get pregnant. And it really takes a little discussion to understand why.
Host: Okay so, genetic carrier screening. Tell us what that is.
Dr. Weckstein: There’s a huge explosion in recent years in our knowledge about genetics. We all carry in our genes, some genetic diseases. In recent years, we’ve been able to test for more and more genetic diseases in a very cost effective manner. And there’s a couple of common categories of genetic diseases to talk about today. One is called autosomal dominant diseases. And these are genetic diseases the you will transmit to 50% of your offspring if you carry that disease. Carriers are affected by the disease, so they usually will show signs of having that disease themselves. These diseases are typically seen in your family history, so just from knowing if there’s a major disease in many family members throughout generations; you can suspect that you may carry this disease.
And examples of autosomal dominant diseases that patients have heard of include myotonic or muscular dystrophy, and Marfan’s Syndrome. A second type of disease that we want to talk about are autosomal recessive disorders. And these are often not seen in family history. Carriers of this type of disease are not usually affected by the disease themselves so, both partners need to be a carrier of the disease in order for their child to actually have the disease. There could be multiple members of your family who carry this disease but are unaware of it because their reproductive partners were not carriers of the disease, so there are no children with the disease in the family.
But if both partners carry an autosomal recessive disease, then 25% of their children will have the disease. Examples of this type of disease that people have heard of include cystic fibrosis, thalassemia, and Tay Sachs. And genetic carrier screening typically screens for these autosomal recessive diseases that people are usually not aware that they carry because there is nothing in their family.
Host: Wow. I keep thinking of that PSA you see on TV, the more you know. Wow, what a benefit that would be. A benefit and potentially scary for people too like I don’t want to know, so I don’t want to do this. So, it really presents some interesting questions. So, then why should you do screening for genetic diseases before you plan to get pregnant?
Dr. Weckstein: Since all of us carry some genetic diseases; if both you and your partner unknowingly carry the same autosomal recessive disease; then 25% of your kids will be affected by that disease. Current genetic carrier screening panels which are blood tests, can screen for hundreds of diseases and data or studies show that about one and a half to two and a half percent of couples who are of similar ethnic origin will be carriers of the same genetic disease when they are screened with one of these extended carrier disease blood panels.
If it is determined that both partners are carriers of the same genetic disease; then you can use preimplantation genetic testing the embryos with IVF treatment in order to prevent having a child with the disease. So, really great powerful knowledge to have before you do an IVF treatment.
Host: All right so you just mentioned preimplantation genetic testing again, so then why should you do genetic carrier screening if preimplantation genetic embryos routinely picks up these diseases.
Dr. Weckstein: Excellent question. The answer is that the common form of PGT or preimplantation genetic testing of embryos screens all 23 chromosomes for an abnormal number of chromosomes. Embryos in all of us should have two copies of every chromosome. An example of an abnormal number of chromosomes would be a Down Syndrome child who has three copies of chromosome 21. When we do routine IVF and preimplantation testing of embryos; we only have a very small amount of DNA genetic material that is given to the genetics lab to do the testing.
So, testing can be done for all the 23 chromosomes, but we can’t test for 250 or more diseases that can be tested in the blood genetic carrier screening panel. If we find that both partners carry the same disease with the genetic carrier screening blood panel; then we can direct the genetics laboratory to test this small amount of DNA or genetic material specifically for the disease that the couple carry.
Host: So, if a couple has a positive test for a certain disease, high probability; what happens then? Does a couple say, you know what, we are not going to have kids or how do you - what happens? Do you monitor them. I’m just curious what happens in that situation?
Dr. Weckstein: That’s an excellent question and that’s exactly why we can now do this testing so normally, if a couple knew that 25% of their kids would have a bad disease; then they would have the option to say okay, we don’t want to take that chance, we are not going to get pregnant or that we’re going to try to get pregnant on our own, accept that 25% risk and there is testing that a couple can do early on in a pregnancy, amniocentesis or chorionic villa sampling that will pick up does this pregnancy have that disease, 25% will and they would know about that ahead of time or, they can do preimplantation genetic testing of embryos and know that approximately one out of four of their embryos will carry that disease and then we just do not transfer the embryo that carries that disease.
We only transfer an embryo that does not carry the disease. So, they can reduce the chance of having a child with that abnormality or that disease from 25% down to almost zero.
Host: This is truly amazing. Amazing. So, as I mentioned earlier, for some people, maybe this is great, let’s do it and other people nah, this is scary, I don’t want to know. So, I’m just curious how common is it to have IVF patients doing PGT for genetic diseases?
Dr. Weckstein: We see a lot of patients in our practice who do not have fertility problems. They have no trouble getting pregnant. Probably one or two patients every week, but they are doing IVF with genetic testing of embryos because they already have a child who is found to have a severe genetic disease. And after they found that they had a child with that genetic disease, then they did testing themselves and were both found to be a carrier of that disease, so they knew wow we had that one out of four chance, we had that baby with a genetic disease so with no fertility problem at all; they are now doing IVF with genetic testing of embryos to prevent having another child with that disease.
And given the tragedy of having a child with severe disease that could have been prevented by having the knowledge ahead of time that both partners were carriers of that disease before they even planned for pregnancy; that’s a strong reason that we recommend patients do genetic carrier screening before pregnancy and before starting infertility treatment.
Host: So, this sounds so beneficial. It sounds like even for those couples who aren’t having a hard time getting pregnant they would benefit from this type of testing too. Is that right?
Dr. Weckstein: Correct. And it’s just blood tests that for 200 to 250 dollars you can test for 300 different genetic diseases. So, if you know heh, when my kids want to get pregnant, I’m going to tell them for sure do this testing ahead of time because if you find you’re both a carrier, you should then do IVF treatment to screen out embryos that have this disease.
Host: This has been amazing and so informative. Thank you so much Dr. Weckstein. We really appreciate it. And to get connected with Dr. Weckstein or another physician, please visit www.rscbayarea.com. And if you found this podcast helpful, please share it on your social channels and check out our entire podcast library for topics of interest to you. This is Fertile Edge by Reproductive Science Center of San Francisco Bay. I’m Bill Klaproth. Thanks for listening.
