Cheryl Martin (Host): There are various options couples explore to build their future families. Coming up, we take a closer look at one of them, elective embryo freezing, also known as cryopreservation. Here to answer some of the most common questions about this option, is Dr. Mary Hinckley, the IVF Medical Director at the Reproductive Science Center of the San Francisco Bay Area.

 This is Fertile Edge, a podcast from the Reproductive Science Center of the San Francisco Bay Area. I'm Cheryl Martin. Dr. Hinckley, so glad to have you on to get some of these answers.

Mary Hinckley, MD: Well, thank you, Cheryl. I am so happy to be here today and to talk to a wider audience about some of the things that I get asked constantly in my office because this is such a hot topic right now.

Host: Why would someone consider embryo freezing or cryopreservation versus egg freezing?

Mary Hinckley, MD: Well, it's interesting. When we go back to think about what we do best in our field, we freeze embryos really well. Freezing eggs is a newer thing, and we've gotten very good at it, but eggs do not freeze as well as embryos, and that has a lot to do with the water content of the egg versus the water content of the embryo.

Just like if you were putting a Coca Cola bottle into your freezer and it would explode because there's a lot of water in it, versus putting a piece of paper in your freezer, which doesn't change. The same thing is similar in terms of the egg, which has a lot of water, versus an embryo, which we've usually dehydrated to a certain degree before we freeze it.

So for the reason that embryos freeze better, we've been doing it for longer. We have great outcomes on embryos that have been frozen and then warmed and then turned into beautiful, healthy babies. There is a draw towards freezing embryos, um, when people come, the biggest problem is some people don't have a sperm provider to be able to make those embryos.

And so in those situations, we do think more seriously about eggs because they are not ready to commit to the sperm provider or haven't yet found that partner that they want to be with for the rest of their life.

Host: So, how many embryos do you need to freeze?

Mary Hinckley, MD: Well, that's an interesting question, and that probably has to do with the quality of the clinic and what your goals are. Now, sometimes I see patients that want to be able to have one child, and they're still maybe deciding whether or not having one child is even right for them, but they don't want to lose out on that opportunity.

And so, in our clinic, where a frozen embryo generally has a success rate around 69 percent of being a baby, we can freeze one or two. And if they want more security, we might prefer to try to make three. So the statistics out of our clinic show that one frozen embryo, especially if it's been tested for chromosome problems and found to be free of any chromosomal diseases, will give you a live birth rate of around 69%.

If the first one doesn't work and we try again, that will give you a cumulative success rate of around 84%. And if that still didn't work, and we tried again, and now we've tried three times, that gives you a cumulative success rate of around 90 to 92% chance of having a baby. So for a lot of women, a 92 percent chance of being able to have one child is very reasonable.

We can never be 100%. We are not in control of all of this. There is a lot of mystery, um, that goes into making a baby. And so 92 percent is very reasonable and many patients will accept that. But the problem comes, what if they want two children? Or what if they want three children? Or what if they don't know if they're going to be able to have the first child on their own without any reproductive help, but then maybe by the time they're ready for the second or the third, that they might want to be able to access the embryos they've frozen.

So for that reason, a good consultation with their doctor about what their goals may be, even though they might change over time, is a great starting point. Because then we can set up the situation of if then and make sure that they've covered themselves to the best of their ability to be able to have more choices in the future for building their family the way they want it at that time.

Host: Now, here's another question. What is PGT testing and should I do it?

Mary Hinckley, MD: Yeah, that is a good question. And I think for a lot of people that are choosing to do embryo banking or embryo freezing for the future, electively, that doing PGT A testing, which stands for pre implantation, genetic testing for aneuploidy or abnormal chromosomes is a great idea. It's the best technology we have today to tell you if your embryo has a good chance of being a healthy baby.

It is not perfect technology. And over the next five to 10 years, we may have better technology. But if you're coming to me today as a 32 year old woman, hopefully ready to have a family maybe in the next three to four years, but hoping to have two children or three children, then using the PGT A testing to find out if that embryo is normal will help us know better how many embryos you need to have in the bank.

So not every embryo will be a baby even if it's normal. But if it's not tested, there's a much greater chance that that embryo will not be a baby, that it might be chromosomally abnormal and therefore never implant or miscarry. And so if someone is banking on that embryo for the future, it's really helpful for them to have a sense of what are the chances that that embryo is normal.

Now, if they choose not to use this technology because they think maybe something new is going to come down the line, or they're not okay with only being 98 percent certain that a normal embryo is really a normal embryo, then we just have to use a calculation to figure out how many embryos to freeze.

So, for example, if you're a 38 year old woman, and you want to have one chromosomally normal embryo to transfer. We know that about 50 percent of your embryos are going to be chromosomally normal that make it to the blastocyst stage, the stage where we freeze them. So for that reason, I would advise a 38 year old woman to have two embryos for every, you know, for the fact that they might expect to have one being chromosomally normal. So if we take a couple who is freezing embryos for the future and they don't know if the embryos are normal or not, for many of them, they have to have two to three times as many embryos

available to use to expect to have at least one of those be normal. And so again, it helps to have more knowledge about that embryo when you freeze it. If you know, I have three chromosomally normal embryos, then I know that I get three chances at a baby and I get around a 92 percent chance cumulative, that at least one of those will be my child.

And so it gives more certainty to what you're banking for the future. It's not necessary to do, but it is the best technology we have today to let you know, is that embryo normal? One of the other things that I like to explain to patients is many women do not make a lot of chromosomally normal embryos in a single cycle.

And so oftentimes they're faced with the decision of, do I want to do this again? Now, some people can only afford to do it once or only want to do it once, but there are some people, especially in the Bay area who have, um, work in tech and have great insurance that will allow them to do up to three cycles. And for these women, if they were hoping to have one child in the future, and in a single cycle, they made three chromosomally normal embryos, they could be done, finished, and feel like they have good odds, not 100%, but good odds. On the other hand, if they didn't test the embryos, then we don't know if those three embryos are going to be normal.

And so therefore we might say you need to have six or you need to have nine. And so they might then need to do a second or a third cycle; when in essence, their first cycle, really got them all the embryos they needed to get a reasonable chance. So sometimes using the PGT A testing can be really helpful to either allow them to know they need to do a second or a third cycle or to tell them they don't have to do a second or a third cycle.

Host: Thanks for explaining that very, very clearly. Now, here's another question. If I'm ready to get pregnant, should I try on my own first or should I use the frozen embryos as they may produce a healthier baby?

Mary Hinckley, MD: Oh, I love this question and this is so hard to know the answer to, but I have a lot of fun talking with patients about this. So let's say for example, I have a 30 year old patient who's newly married and she and her husband know they want children and she's going to be in med school for the next four years or residency.

And they say, okay, when I get out, I'll be 34. And that's the time I maybe want to think about starting my family. So should I try to get pregnant on my own at 34? Or if I was able to freeze chromosomally normal embryos, are those embryos better? That's the question I get asked a lot. And so my answer is depends on what your chances are of miscarriage at the time.

So if we've done testing on the embryo, we've lowered your miscarriage rate to around eight to 10 percent with the embryos in our clinic, based on our testing. So if you're 34 and you're trying for the first time, your miscarriage rate is around 25 percent to 30 percent and so for some women, some couples, trying to get pregnant naturally and having to go through either some months with it doesn't work or go through a miscarriage, that can be really hard physically, emotionally, and for a lot of women, they would rather use the embryos they've frozen because the miscarriage rate is lower.

However, I want to be very clear to tell them that the baby born from IVF with PGT testing is not any healthier than the baby born when you get pregnant on your own. Because once you get to the baby, we've already weeded out all the miscarriages. So if we're saying, here's a baby born from IVF and a baby born from a natural conception, those children have equally good chances at being smart and beautiful and having lots of friends and achieving all their goals in life.

There's no difference, in that, at that point. The difference comes in the embryo because an embryo that implants naturally inside your body that has not been tested for chromosomal abnormalities has a higher chance of miscarrying, whereas an embryo that's already been through testing has a lower chance.

And so, if a woman is 34 and wants to start, 25 percent chance of miscarriage is pretty normal. If they feel like, you know what, I got a 75 percent chance that when I get pregnant, it's my baby and I don't want to spend more money or use those embryos yet. I want to save them for later. Many of them will try on their own for a set point period of time.

However, if someone comes to me at 40 because they got sidetracked or things happened, I might say your miscarriage rate at 40 is 50 percent and that will take up time and energy and you might rather use the embryos that have been frozen that are tested and normal and have a miscarriage rate of around eight to ten percent.

So we can always make that decision when we get there, but oftentimes I tell patients, you know, it really depends on when you decide to start trying and what your miscarriage rate based on age, because that's the most important determinant is at that time.

Host: Now, you have mentioned extra embryos, so here's another question. What do I do with the extra embryos after I have finished my family? I have my two kids. I have my one kid.

Mary Hinckley, MD: Well, it's good that you're thinking about that now, or knowing that some of the listeners are thinking about that because I think a lot of people, especially if they come in with a lot of the fears and the concerns about, am I going to be able to have a family? And am I going to be able to have all the children I want, especially my patients who have had some infertility, they don't really spend much time thinking about what happens after I've been able to have the family that I desired.

And for many people, it becomes a much harder decision than they realized because they maybe are looking at a child that came from an embryo that they had frozen and they love that child and they know how wonderful it is. And then they look at what we call a sibling embryo or an embryo that was frozen at the same time and had the same potential.

And to discard that embryo becomes much more challenging and sometimes it even becomes something where the husband and the wife or the two partners feel different about and one maybe is okay with discarding, maybe the other partner is not okay. And so this can be a decision point that's hard. I do encourage patients to think about this at the front, um, before they get here to make sure that they're not freezing a lot of extra embryos that might cause some decision making points that are not as easy to get through later.

People will have choices and the choices that they will have are either to discard the embryos saying, thank you for being there, for being an option, for allowing me to have that safety, but, but, we're not needing you anymore. Um, or they have the choice to donate them. And sometimes you can donate them for research that would not result in a child, but research programs are very limited right now because there are so many frozen embryos.

And so the other way to donate them would be to donate them to a couple or an individual that would receive the embryo and use that to create a pregnancy. So this is much like adoption at the level of an embryo. So we call this embryo donation and legally it's different than adoption. And you're in charge of the embryo from the moment you get it and carry the pregnancy, et cetera.

So for some couples or individuals to donate embryos for embryo donation is a better option because they feel that it's honoring that embryo and giving it a chance. So those are the options that you would have down the line. Right now, especially in California, that is your choice. Um, I know people across the country are nervous about whether that really would be their choice and what choices they would have.

And I really feel for people that are at that place. And at that time where they feel like they um, went in with one expectation and now there might be different where they didn't understand it and know how they would feel. And so my heart goes out to them. So I do think it's important to think about this at the beginning and be able to think through what would I do?

And are we on the same page if you have a partner? Um, so that it can make it easier at the end when you've been able to have the family that you dream of.

Host: Dr. Mary Hinckley, such great advice. Thank you so much for addressing some of the most common questions from couples who are exploring embryo freezing. Very informative.

 It is.

Mary Hinckley, MD: Well, thank you for making this possible so that I could get the word out to as many people who are asking this question and maybe even too scared to come into the office to talk about, but we're here. We love to talk to patients about these things and I hope I've given some ideas and some things to ponder for the people listening.

Host: You have. Now you can call 888-377-4483 to learn more and schedule an appointment with an RSC Bay Fertility Specialist. And if you found this podcast helpful, please share it on your social media. Be sure to check out our podcast library for other topics of interest to you. This is Fertile Edge, a podcast from the Reproductive Science Center of the San Francisco Bay Area. Thanks for listening.