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- Genetic testing prior to pregnancy - Fertile Minds video
Genetic testing, explained
Genetic testing prior to pregnancy. So what are the options? Welcome to Fertile Minds.
I'm Dr. Ben Kroon, fertility specialist, reproductive endocrinologist, obstetrician and gynecologist with Queensland Fertility Group. And today I'll be speaking to you about genetic testing, before you fall pregnant.
People always find genetics very confusing. So I'm gonna see if I can lay it out for you in a way that will hopefully help you understand, will help you understand the options available to you and whether or not they're tests that you should consider taking up.
So when you think about genetic disorders, these things are very common. So about 1% of all pregnancies are born with a genetic disorder. And some of these are things, conditions that are inherited. So there are things that are passed down from your parents to you and then potentially pass down to your children. And others are disorders that are specific to the pregnancy. And when I say that what I mean is, when the egg and the sperm come together and create a pregnancy, sometimes errors are made, which means that the pregnancy is genetically abnormal. So these are things that where there's no actual family history of it.
So your genetics in the past may be entirely normal, but in fact, just the way that egg and sperm have come together, they've come together in abnormal way which creates an abnormal pregnancy that has a genetic disorder.
A common example, that might be Down syndrome, for example. When in fact the risk factor is just maternal age. So we know at age 25 when you're young and you try to make babies, your chance of having a baby with Down syndrome or trisomy 21, that's an additional chromosome number 21, it's actually really low, because the chromosomes inside a woman's egg at age are really very effective.
The woman's egg is very good at it. The chromosomes splitting apart and the right number of chromosomes going into each egg. So chances of having an egg with too many chromosomes is very low, but when you're at age 40, for example, the chance of that happening is much, much, much higher. So we know that there's more chances of miscarriages and more chance of genetically abnormal pregnancies. Again Down syndrome is the one that people know most commonly. And we also know that it can be tested for in pregnancy.
So what kind of testing can you do for these kind of disorders, the two groups of disorders, and are these tests right for you? Well, the first thing we'll talk about is the type of testing for disorders that are passed down within families. So these are often what we call recessive conditions and they can occur in families without you even knowing if you have these in families. So common one that people talk about a lot of cystic fibrosis. So in the Caucasian population about one in 20 to 25 of us actually carry this gene.
It's a very, very common and I could carry the gene. I don't know if I carry the gene. I don't know if my wife carries the gene. I don't know if my kids carry the gene. But what I do know is that neither of my kids have inherited two genes, 'cause they do not have cystic fibrosis. So a cystic fibrosis, you can carry a gene. And it doesn't mean anything to you. If your partner carries a gene, again, they might not know they carry a gene, but if both of you carry a gene, and create a pregnancy, then one in four of your pregnancies will actually get that disease. So they'll inherit two genes.
And that's a situation that you obviously want to avoid because no one wants to have a baby with a significant health abnormality, like cystic fibrosis, which causes a very nasty lung abnormality.
Another common one that causes a nasty medical condition in children is spinal muscular atrophy. It causes a neurological condition, severe neurological condition. Again, it's not a problem if you carry a gene and you'd never know if you carried a gene, but if you carry a gene and your partner carries a gene then one in four of your babies has a risk of getting that disease.
So if we think about those genetic conditions for example, cystic fibrosis, can we test for them? Well, we can. And for years these tests have been too expensive, and out of the reach of the general public but now they're tests that we can do, and do at a relatively cheap cost with no risk to the person having the test. And I'd offer them to every single patient.
And to be honest, if I was getting pregnant, sorry, not if I was getting pregnant, if my wife was getting pregnant, we're planning a baby, there's a 100% recommendation would be that I'd say have one of these tests. So simple blood tests can detect three genes, fragile X, spinal muscular atrophy, cystic fibrosis. Three that cause really significant conditions. For a few $100, a blood test can be done to detect if you carry the gene.
Now, if a person has this test and they do not carry the gene, then there's no way that no matter what their partner carries, that they can have a pregnancy that carries that condition because you'd have to have both the male and female partner carry the gene for an offspring to have the disease. So if one of your test negative, that's fine. You can't have a baby with those diseases.
Now there are tests that actually tests for many more diseases. So I've just mentioned the three most common one, but we've got a test that can test for about 550 odd diseases. It's a huge number of diseases, amazing test. Of course, the more you test for the more you're likely to find. So high number of people actually come up with a positive test for these conditions that are sometimes very rare. But again, if you come up with none you've excluded a huge number of conditions that a child would otherwise have the risk of being born with.
So having tested for those recessive conditions, let's say you want to go ahead and try to conceive. And in this circumstance, let's say we're talking about conceiving by IVF. The question that I'm often asked is, what about those things, those genetic conditions that have nothing to do with the genes that you may carry in your family, but has to do with what I was talking about earlier, which is things like Down syndrome, where it's all to do with errors and the egg and the sperm coming together.
And in particular, those areas that are associated with age, can we test for those? Well, you can, with IVF, you can do a thing called pre-implantation genetic screening. And then this is a very high tech method of basically taking DNA from the embryo, taking that DNA outside of the embryo, freezing the embryo, testing the DNA to find out the genetic composition of the embryo. And then once we found out the genetic composition of the embryo, we can then say, hey, that embryo is good or no, that embryo has got an abnormality.
So this is amazing technology, and an IVF cycle is undertaken, the embryo is grown to about day five of embryo growth. And at that point the embryo is big enough to sustain lasering a hole in the side of the embryo, a very small microscopic hole.
Some cells are taken out, the embryo is frozen and those cells are transported to a genetics laboratory where it's carefully tested for a genetic abnormality. And as I said, feedback is then given about which embryos are normal and which embryos aren't normal.
Now, this technology is not for everybody, of course. And when we see patients we spend a long time talking with them about the pros and cons of genetic testing embryos. And for some people it's not the right thing to do, but for other people, particularly people who may have recurrent pregnancy loss or people who make multiple embryos and continually having embryos put back but maybe those embryos aren't implanting, it might be worthwhile to genetically test whether those embryos are normal or not normal.
And certainly I've got a lot of patients who've had maybe a child with genetic abnormalities such as Down syndrome, or indeed who may have a genetic abnormality that's been detected. So they might have something that runs in their family a specific gene, for example, cystic fibrosis. And in that circumstance, they might've known for some time that they carry a cystic fibrosis gene or a gene for another abnormality. And in that circumstance we can actually specifically test that embryo to see if that gene has been carried. Does their embryo carry the cystic fibrosis gene? Does it carry some other inherited gene that's come down in the family line. So in that circumstance, we can test that embryo and absolutely we get a lot of people wanting to do that.
Great technology and very successful outcomes. So after listening to this, if you suspect you may have a genetic or chromosomal abnormality, make sure you see your GP or your fertility specialists for support and investigation. They can organise genetic counseling and tests and help you decide what's right for you.
So thanks very much for watching. At Queensland Fertility Group, we're always happy to speak to you about your individual circumstances. Be sure to leave a comment below and don't forget to subscribe (to our channel).
*All opinions expressed on the Fertile Minds YouTube Channel belong to the individual doctors, scientists and specialists, not the Virtus Health group.