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She transferred mosaic embryos
Tests showed her embryos might have chromosomal problems. A woman tells me what it was like to transfer them anyway.
Many people now do preimplantation genetic testing for aneuploidy (PGT-A). The test purports to determine whether an embryo has the correct complement of chromosomes.
PGT-A involves plucking five or ten cells from the 100-odd cells in a blastocyst-stage embryo. The cells are taken from a part of the embryo that will go on to become the placenta, but the presumption is that the findings also represent the part that will go on to become the fetus.
Each cell's chromosomes are counted. Sometimes all the cells have the correct chromosomes, and so the whole embryo is declared "euploid," or good. Sometimes all the cells have abnormalities, so the embryo is deemed "anueploid," or bad. But sometimes it's more of a mixed bag, with a few good cells and a few bad. That is a "mosaic."
In the early days of testing, people didn't know what to do with these. Often, they were tossed. But slowly, a few people, who had nothing but mosaic embryos to work with, decided to risk transferring them. Some of those led to live births and apparently healthy babies.
It's still controversial. Many doctors will not transfer them. But some will. The logic is that if the chromosomal error is genuinely there, the pregnancy will end in miscarriage. And if, for whatever reason, the cells tested were not good stand-ins for the cells that will go on to become the fetus — there are various theories about why this could be — then the baby might be okay.
Recently I spoke to a woman who decided to transfer her mosaic embryos. Here's her story.
14 minute read
Let's start at the beginning. You decided you wanted to become a parent...
I decided I wanted to become a parent shortly after I got married, which was 10 years ago.
And the routine way didn't work?
We had tried for 18 months. Then we started with a very large, well-known clinic here in the Chicago area. We started doing IUI — my health insurance did not cover IVF. I think we did one round of IUI, and it didn't work. I was actually in the middle of another round when I had to go to a business meeting in another part of the country and that kind of messed up the cycle. Ironically, I ended up getting pregnant naturally.
So I had my first child in 2016. I was 37.
Okay. So you wanted another child...
This is where the story gets fun. Five or six weeks after delivering, I found out that I had a substantial amount of retained placenta, so I had to have a D&C [dilation and curettage, which removes tissue from the uterus]. And, literally, the first time my husband and I had sex after the procedure, I got pregnant. I got pregnant when I had a three-month-old.
Two girls, one year apart. They actually have the same birthday. It was a bit insane, but it was fun. Then we kind of stopped trying. I was traveling for work. It was just one of those things where we'd love to have another kid, but if we did, we really would only want a boy.
In 2020, right at the beginning of COVID, I started a new job. My new insurance covered IVF. I was 41. And we decided to try for a son.
I went in and the doctor gave me a 15 to 20 percent chance of even being able to get pregnant through IVF with my eggs at the age that they were. But we did one round of IVF in October of 2020, and I responded incredibly well to all of the stims. We ended up having five embryos biopsied for PGT testing. And one embryo came back as euploid. And it was a little girl.
And the doctor was like, 'Yeah, your insurance isn't going to cover another round. Because you got one normal embryo.'
So if you hadn't gotten that one, they would have paid?
Yeah. I mean, I get it. They're doing this because we're having trouble conceiving. They're not paying for us to get a boy.
So we decided, let's put her on ice and think this through. I felt very blessed at my age to get a euploid at all. And so after a few months, I said to my husband, 'You know what, let's just put her in and see what happens. If we were meant to have three girls, we were meant to have three girls.' She was born in 2021.
Oh. This is a different story than I was expecting!
Yeah, this isn't I'm-32-with-a-mosaic-trying-to-get-one-baby. This is — I'm a machine over here!
But when does the mosaic come in?
So I had five months of maternity leave at that point. We decided to try again. I went back to the same clinic. They wanted me to wait a year, but I'd just turned 44 and I'm like, I don't have a year. So they agreed, and we started doing all the pre-testing and everything. And sure enough, my insurance would not cover anybody over the age of 44.
You just missed the cutoff?
I turned 44 in March, and I started back at the clinic in April.
But ironically, while I was on maternity leave, I got recruited by another company, and I ended up making a move, completely unexpectedly, in May of 2022. And my new insurance didn't have an age restriction on IVF. It's like this job came to me so that I could have a son.
So you gave it another try?
We did a round last October. I got 22 eggs. Twenty were mature, 17 fertilized and nine made it to day-five blastocyst. So I was like, 'Oh my gosh, we got nine day-five blasts — there's bound to be a healthy boy in there!' Three weeks later, I got the email. 'We regret to inform you that eight of your samples were aneuploid and one was a mosaic monosomy 1 and monosomy 22, which is not eligible for transfer.'
Monosomy means only one chromosome where there should be two. So your PGT testing found that this embryo was missing a chromosome 1 and also a chromosome 22. How serious was that?
I don't think it could result in a live birth. Those particular two chromosomes, I remember looking them up. But when I first got the email, I was like, What does that mean?
What did you do?
I called the company that did the PGT testing. They had a genetic counsellor. She explained this whole phenomenon of mosaicism. It's very controversial. She said many doctors won't transfer them because of the risks involved.
That you could have a miscarriage. Or that you might have a child with a serious medical condition.
Right. And then I asked, 'Just out of curiosity, what is the gender of that embryo?' And she said, 'It's a male.' And I lost it. I was like, 'Oh, my gosh, you just said male!' And so she's like, 'Yeah, you know, some doctors may be willing to transfer' — it was a low-level mosaic — 'but some won't.'
Now when you say 'low-level mosaic,' you are talking about the proportion of cells that had that abnormality, right? So they maybe plucked out six cells from your embryo, and two of the six were missing these chromosomes.
What I've learned is that when they code an embryo 'mosaic,' it's 'low-level' or 'high-level.' My understanding is that a euploid, normal embryo has 20 percent or less abnormal cells. Every company does it a little bit differently. But typically, a low-level mosaic, from what I've read, is 30 to 50 percent abnormal. And a high is like 50 to 70 percent. A completely aneuploid, bad, unhealthy embryo is 80 percent or more bad cells.
What was the actual percentage for your embryo?
They won't share it.
I asked. They don't get that granular. Why? I don't know because there's a big difference between 30 and 50 percent.
So I set up an appointment with my doctor. I had a consultation in person with him, and I shared with him what the genetic counsellor had told me, and he got really upset. Because what she told me was the complete opposite of what the clinic's policy was. He's like, you've got a complex mosaic here.
I thought complex was three or more chromosomes affected, but for this clinic it was two.
So he's like, you're crazy to even consider this. And the baby could have all sorts of issues. I was so upset. I was like, 'But she told me...' I went home and told my husband, 'Our dreams are shattered. He's telling me I'm nuts.'
What did your husband think?
My husband got online, and he put in 'mosaic embryo.' And the name of a doctor came up. So did his YouTube videos, all about mosaic embryos, and how he believes that low-level mosaics have an equivalent success rate to a euploid. I'm watching all these videos, and I'm just emotional because this is opposite of what the other doctor told me.
What did you do?
I said to my husband, 'I'm 44. Let me see if I can squeeze in one more round and then that's it, I'm done.' Because I really wanted a son, just to experience having a son. But I also wanted a son because my husband's name doesn't continue. And I'm the most tenacious... I'll be darned if somebody's going to tell me I can't do something, even something that I can't really control.
So you had just done a retrieval in October 2022, and you decided to do a second one in, what, November?
Yes. And I got 25 eggs. Twenty-two mature, 20 fertilized. I mean, it was just some crazy numbers. I think seven of them made it to day-five blastocyst. And I was like, 'Okay, here we go again.' And when I got the results back, sure enough, one euploid female.
And one low-level mosaic trisomy 13 boy.
Trisomy 13. That's serious, right?
At the time, I didn't know what a trisomy 13 meant. I just knew, 'Oh, hey, this guy is not complex. It's only one chromosome, right?' I called my husband, and said 'We got another low-level mosaic, and it's only one!' Again, I didn't know that trisomy 13 was lethal, like, way worse than a monosomy 1or a monosomy 22. Again I had a conversation with a genetic counsellor at the testing company, and she shared with me the details around trisomy 13.
After this happened, I set up an online consultation with that doctor who transfers mosaics. He will only transfer low-level mosaics, not high-level mosaics. He made me feel like I had two really good options with these two male, low-level mosaics. I said, 'If you were me, which one would you transfer first?' And he said, 'Honestly, it really doesn't matter.'
He said the chromosome doesn't matter. They're both low.
Some people say mosaic embryos self-correct. But this doctor seemed to believe that they weren't actually mosaic to begin with.
He goes, 'If you want to, do the monosomy 1 monosomy 22 first' — because it won't survive with that if it's actually there. If you have trisomy 13, you can survive, but my understanding is you usually die within 24 hours.
So you had to get the embryos moved from the other clinic to this new clinic?
Yeah, I did that myself. I picked up the nitrogen tank from the new clinic and drove all the way to downtown Chicago. They put the embryos in, and I drove them back to the new clinic.
How did the old clinic react? Did they try to dissuade you?
So you decided to go ahead and transfer a mosaic embryo. Which one did you pick?
The monosomy 1 monosomy 22. I had the transfer in April.
Were you nervous?
I wasn't. I didn't really think much about it. One of three things would happen. Either it's not going to implant, I'm going to have a very early miscarriage, or I'm going to have a healthy baby. Long story short, it didn't take. I was devastated.
At this point I'm 45. I wanted to transfer the the other one as soon as possible. I think it was May 3 when we did the trisomy 13 transfer.
I had already asked the nurses, 'If this doesn't work, how long do I have to wait to do another retrieval?'
Another retrieval? And not use the euploid?
Well, the euploid was a girl.
I know, but... You changed your mind on that once before.
Yes, you're very right. I did.
I'm so career-oriented. If you had told me ten years ago that I was going to have four kids, I would be like, 'What? You're on something!'
So why are you? What's driving you?
I don't know!! They're all so beautiful. And they're just amazing, right? I mean, every mom says that about their kid. They're all, you know, unique in their own way. God gifted me to have babies at the age of 45. Maybe that's what I'm supposed to be doing.
Anyway, they did this transfer in May of this year. The doctor has you come back in seven or eight days. But naturally, I started testing at day three at home. And it was negative. Day four was negative. Day five was negative. And I just said to my husband, 'I don't think it worked.' Day six, I thought, 'I'm just going to test one more time, and then get really depressed.' But the thing had a faint positive. I went to the clinic two days later and it was positive.
The doctor had said the likelihood of this baby actually having trisomy 13 was one out of 1650. I don't know where he got that from, but he gave me that before I did the transfer, which made me feel pretty confident about doing it.
Has everything been smooth?
Mostly. I was at a restaurant with the family and we were waiting for a table. I just felt a gush of something. So I went to the ladies room and it was like a murder scene — blood everywhere, clots the size of a fist. I'm like, 'Oh my god, I'm having a miscarriage.'
But I wasn't. It was a subchorionic hematoma [bleeding under the membrane]. When I went into the clinic, they saw a heartbeat. Everything was totally fine.
Anyway, fast forward to week 10. I do the NIPT [non-invasive prenatal] testing. It came back negative for trisomy 13,18, 21. Everything was completely normal.
Then I do the 12-week ultrasound. And everything's completely normal.
Because I'm over the age of 35, at 12 weeks I was sent to maternal-fetal medicine specialists. The doctor at maternal-fetal medicine was like, 'You transferred a what?' I could tell by the things that he said, he didn't really know much about mosaicism.
He was like, 'Did the doctor educate you at all on trisomy 13?' And I was like, 'You know, he did.' And I said, 'I felt I could really trust his advice.' My husband almost walked out. My husband was like, 'What's done is done. We've already done it. Please don't scare us for no reason, just because you don't know about the topic.'
The doctor said, 'I want you to come in for ultrasounds every four weeks. I'm going to monitor you even more closely than I normally would.' But now he's, 'You need to speak nationally on this! This is amazing! There's nothing wrong that I see. The baby is perfect.' So here we are.
You didn't have any anxiety about doing this?
No, but I didn't announce the pregnancy socially until the 22nd week. Even though everything was fine and perfect until then.
But I never asked myself, if this baby came back as a positive for trisomy 13, would I terminate it? I don't know. And my doctor had asked me that a couple of times, and I'm like, let's cross that bridge when we get to it. I don't know.
You didn't have counselling? About the decision to transfer a mosaic embryo?
They set up a consult with a genetic counsellor in the maternal-fetal medicine group. And she knew nothing about mosaic embryos.
Literally nothing. My husband's like, 'Why are we sitting here?' I don't want to be rude, but I was educating her.
But didn't she walk you through the scenarios and help with the 'what ifs'?
It was almost like I was the first patient they had ever seen that had transferred a mosaic embryo.
What about in advance of transferring the embryo? You weren't offered any counselling?
The company that did the PGT test offered a genetic counsellor call. I did it twice — for the first mosaic I received, and then I did it for this one. She basically just told me trisomy 13 is lethal. But it wasn't like, 'What would you do if you transferred it and...?' It really never got to that point.
Do you wish you'd had some real counselling?
I don't think it would have changed my decision.
But maybe it would have helped you think through the 'what-if' questions?
My OB was telling me that years ago, she had someone that had a baby diagnosed with trisomy 18. And for religious reasons, they decided to deliver. And the baby died minutes later.
Do you want to put yourselves through that? I think my husband would probably say terminate. But I don't think I would. I don't know. I don't know. The thought of having a baby and having it die within minutes, I can't even imagine what that experience is like.
I said to myself, you got three kids, they're beautiful, they're healthy. If this turns into a miscarriage, I can say that I tried, and it was out of my control.
What do you tell other people who are thinking about this?
I'm in all these chat groups and Facebook groups about mosaic embryos. It breaks my heart to see these women who are being told that they can't transfer these embryos — when they can. I post ultrasound pictures, and I say, 'Give your mosaics a chance.'
I know there's a lot of women out there that have gotten pregnant with a high-level. I don't know if I would have felt as confident doing high-level.
I don't want to say the doctor was wrong. But I'm living proof that it's not as scary as people think or as doctors sometimes make it out to be. I could have easily just taken the first doctor's guidance. We would have discarded. And then I wouldn't be having a son right now.
What's your due date?
Have a great birth.
"Mosaic embryos." HeyReprotech. 03 Dec 2019.
"How often do 'bad' embryos lead to 'good' babies?" HeyReprotech. 17 May 2022.
It's worth noting that the UK regulator's traffic light system rates PGT-A "red," saying that for most patients it does not increase the chance of having a baby.