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Mr and Mrs Peterson

Here Mr and Mrs Peterson attend the genetics clinic to discuss their reproductive options, including the possibility of prenatal diagnosis.
Hello, Mr. and Mrs. Peterson. Lovely to see you both again. How have you been? Well, I’ve got some news which I feel is good news, but it’s causing quite a lot of anxiety. I found out I’m eight weeks pregnant. And we have quite sort of different opinions. But I feel like, you know, of course I’m worried about the effect it’s going to have on me and everything that we’ve talked about before. But I’m worried about the children. I’m worried about Ella and Henry. And then this child, if I’ve passed the mutation on to them and if I pass it on to this child.
But I just feel, well, in some ways it’s taken away a decision that we would have thought about before. You know, do I want more children? And now I feel like well, this has happened, so– OK. OK. So this was an unplanned pregnancy? Yes. OK. I mean, yeah. So that’s where we find ourselves. We weren’t expecting that and given that we are still, all of us are reeling from the news of last time we saw you, my feeling is it’s probably sensible to not pass on this, sort of, you know, not of a nightmare. It’s not like that. But the, you know, this bad news.
I just feel like we should– if we have the power to limit the progressiveness, you know, the continuation of this problem, you know? And it seems sensible to think about it, at least, you know? Whether we keep. You know, I know where he’s coming from. I understand that because I lost my mum and she lost her mum. And obviously, I wouldn’t want to pass that onto any of my children. But we’ve already got two children, anyway. But we already have, yeah. Well, we don’t know that yet. But I feel this is– if I’m pregnant now, then as I said, that takes away that decision, did I want any more children. Because we were thinking about that.
So, my feeling is go ahead with the pregnancy. But you have a lot of worries. You’ve been very worried about passing it on, and– Ah, yeah. Yeah. Yeah. OK. Shall I talk to you about options? Is that what you’d like me to do? Yeah. I think we’re just a bit, we’re a bit lost with it all and so we thought we’d– OK, all right. Before we talk about the pregnancy any further, Mrs. Peterson, how have you been– both of you, how have you been since I saw you last? How did you cope with the news that I gave you about the BRCA gene mistake? Well, obviously it was distressing.
But in a way, I did anticipate it, as well, so it wasn’t a huge shock. Yeah? Of course, it’s not what I wanted. It’s not what you wanted. And then I’ve just been thinking about what’s the best options from there. OK. And have you had an MRI scan yet? No. OK, all right. Has that been booked for you? Yes. OK. [INAUDIBLE] And then my feeling that yeah, I’ve just been a bit– we’ve both been knocked over by it. But it feels– Of course. –keep going if it wasn’t for Angelina Jolie doing her thing we wouldn’t be here. So it’s a bit, you know, it’s all good but it’s somehow terrifying, as well. You know– Of course it is.
Of course it is. Yeah, yeah. Of course it is. Let’s talk about this pregnancy because I know that that’s what’s causing you most anxiety at the moment. And I know that you’ll remember from when I saw you previously that we talked about the 50/50 risk of you passing a gene mistake onto any of your children. And that risk applies to Ella and Henry and obviously, also, applies to this current pregnancy. Now, we don’t test children for this gene mistake because having a BRCA1 or BRCA2 gene mistake isn’t something that affects children. It only effects adults. And we don’t test children for adult-onset diseases.
So we wouldn’t test Ella or Henry for the gene mistake until they’re at least the age of 18. But you wouldn’t need to test Henry anyway because he’s a boy, isn’t that right? Henry has a 50/50 chance of inheriting the BRCA1 gene mistake from your wife. And Henry’s a boy so he doesn’t have any ovarian tissue, does have a small amount of breast tissue so he will be at an increased risk of breast cancer if he inherits the gene mistake. He’ll also be more likely to develop aggressive prostate cancer if he has the gene mistake. And equally, if Henry has the gene mistake, there will be a 50/50 chance that he can pass it on.
So that’s something that we’d need to talk to Henry about and Ella, of course, at the appropriate time. But today, let’s just go back to the pregnancy. So we know already that the pregnancy has a 50/50 risk of inheriting your gene mistake. And the pregnancy can be tested for that gene mistake, if that’s what you’d like. And again, there are a couple of things that we can think about here. One thing that we can do is what we call a non-invasive test in mum. And that’s when we take a blood sample from mum that allows us to determine the sex of the pregnancy. That will tell us if the pregnancy is male or female.
Because BRCA gene mistakes tend not to affect men, tend only to affect daughters or girls, women. Sometimes people say, well, if it’s my son that’s got a BRCA gene mistake, I don’t mind. We’ll carry on. That’s a noninvasive test because it doesn’t invade the pregnancy so there’s no risk of miscarriage. If we found that the pregnancy was female, some people would then say I want you to go on and test the pregnancy to see if the pregnancy’s inherited the BRCA gene mistake. What we do then is an invasive test in pregnancy. There’s always a miscarriage risk with invasive tests in pregnancy. And you may have heard about tests in pregnancy from your previous pregnancies.
Is it something you’ve heard of or know anything about? Yeah. And absolutely, as you say, that that would increase my risk of miscarrying. So the risks of miscarriage are– there’s two types of invasive tests. There’s the placenta testing test, or the CVS test, that’s done quite early in pregnancy, normally at about 10 weeks. And the risk of miscarriage with that is approximately 2%. The amniocentesis test is done a little bit later in pregnancy, normally at about 14 weeks. And The miscarriage risk of that is 1%. In both tests, a sample is taken using an ultrasound and a needle going in to either the placenta or the amniotic fluid.
And that sample is tested to see if the gene mistake has been passed on. And it takes approximately three weeks for those results to become available. And that’s something you need to factor in– if you’re having a test, if you are going to think about terminating the pregnancy with an unfavourable result. I don’t want to terminate the pregnancy. Yeah, but it would make sense to have tests. I mean, that’s not– that’s not perfect. You know, it’s the bit before, isn’t it? Any decision about termination comes after the tests, doesn’t it?
What we normally counsel people to do if they’re having an invasive test in pregnancy, so one where there is a small risk of miscarriage with the test– we counsel them that if the result is unfavourable that they need to have very strongly considered terminating that pregnancy. And there’s many reasons for that. One of which is putting what could be a healthy pregnancy at risk by doing an invasive test. And the second is more of an ethical dilemma. Because if a couple continues with a pregnancy knowing what the gene result is that child could potentially grow up knowing its genetic information without having consented to it.
Then it’s not worth me having the test. It’s not– it’s not worth it. Ah, yeah.
All right.

Mr and Mrs Peterson attend the genetics clinic to discuss their reproductive options.

Please note: Mr and Mrs Peterson are fictional characters invented for teaching purposes, and these clinical scenarios are designed to exemplify teaching points, rather than represent what would occur in the genetics clinic. Any resemblance to any real individuals is purely coincidental.

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The Genomics Era: the Future of Genetics in Medicine

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