What is PGT?

Being a fertility patient is like learning a new language. It’s almost like you have to adopt a new vocabulary of only three-letter words. I do a lot of teaching with my patients, so it’s not required to know everything ahead of time. I encourage patients to come to the office with questions after a Google search. While Google can reveal some scary and worst-case scenarios, it’s a nice primer for helping someone understand the basics and then come to me with specifics. I’m hoping this article will show up in google searches about PGT to inform people the way I inform my patients.

While I always encourage people to do self-study, I think it’s most effective when combined with a conversation with your doctor. It’s easy to self-diagnose, but that’s not effective. It can create anxiety, and it can be based on information found online that’s either not true or doesn’t apply to your specific situation. Please be mindful of this.

Let’s jump in.

PGT = Pre-Implantation Genetic Testing

When I talk about this to patients, one of the first reactions I get is that they think it’s associated with a 100% pregnancy rate and a perfect healthy baby. The other myth I hear is that most think they don’t need it because they don’t have anyone in their family with chromosome issues. Both of these statements are myths. PGT is the closest thing to a crystal ball we have right now but it’s still murky. It’s the best that science has to offer to give us the highest chance for a healthy pregnancy but it has limitations: it only screens chromosomes, not genetic diseases, birth defects, or genes for autism.

Most of my patients, after learning more about it, see the value in considering genetic testing before implantation.

Here are the questions we’re going to cover:

What is PGT?
How is PGT done?
Who should consider PGT, and when?
Are there any risks with PGT?
What are the benefits of PGT?
Why would I want to consider PGT?

First things first. You have to know that just because you have a blastocyst ( 5 or 6 day old embryo with hundreds of cells) that’s beautiful on the outside, doesn’t mean that it has the genetic integrity to turn into a healthy pregnancy.

It would be nice if embryos were exactly like diamonds, but they’re not. Blastocysts may get scored as diamonds do, but the look alone doesn’t indicate the chromosomes are normal. You can’t determine that without doing PGT.

If someone tells you that your embryo is beautiful it does not necessarily mean it will implant and develop into a normal pregnancy. Outside characteristics are not indicative of normal chromosomes.

For someone that’s thirty-five years old, they will get on average about five blastocysts and the percentage chance of each having normal chromosomes (aka euploid) is 80%.

If you’re forty-two years old the average number of blasts in each cycle is one and the chance that it is euploid is 10%.

I want you to know this information now so you have the right set of expectations about what may happen in your cycle and you can go into it with your eyes wide open. This isn’t to suggest we all need to get pregnant when we’re twenty-five when we have the healthiest eggs. No. That’s not going to happen. But we do need to be aware of how our fertility declines with age.

If you’re struggling to get pregnant figure out what your fertility diagnosis is. You’ve likely heard me mention it before, but getting your TUSHY checked is a simple way to remember the steps.

Know what your chances are at your current age and determine if PGT will be helpful for you.

What is PGT?

It used to be called PGS.

PGT-A: This is preimplantation genetic testing for aneuploidy (abnormal chromosomes). Most people don’t have living family members with chromosomal issues. That’s why we test this stuff. It has nothing to do with anything you could have inherited — most of the time. Learn more about PGT-A.

PGT-M: Preimplantation testing for monogenic diseases. For example, you do a carrier screen for 300+ diseases and you find out that you fell madly in love with a guy who is also a carrier for cystic fibrosis. Or you fell in love with a sperm donor that is a carrier for the same disease that you are. So what do you do? You do PGT for that disease. This involves genetic probe creation for the disease that can then be used to screen your embryos. Learn more about PGT-M.

PGT-SR: Preimplantation genetic testing for chromosomal structural rearrangements. If someone has an extra piece of a chromosome in their DNA then you can do your best to screen the embryos for that. You want to determine which embryo is normal and which is not. Learn more about PGT-SR.

What’s the important thing to know here? PGT tests are to look for chromosome issues. In certain cases, also for diseases. It is not a crystal ball. The scientific technology is good, but it is far from perfect. I’d love to learn about genes as it relates to implantation. I’d love for it to be even more detailed, offer more information and sensitive enough to screen even the smallest DNA issues, but it’s not there — yet.

How is PGT done?

Three days after the egg retrieval we do something called assisted hatching to get the embryos ready to be biopsied. I have some patients that question the assisted hatching of the embryos. I compare it to removing your appendix. It can only happen through surgery. Likewise, we can only genetically test an embryo if we hatch it first, and then use a laser to do the biopsy. This is where you’re removing a few cells from the shell of the embryo and sending them to a genetic testing company. The embryos get frozen after the biopsy and a report is generated (called a freeze report) that describes the quality of each embryo. You get the results back from the genetic testing company typically one week later.

Click here to watch a terrific video that demonstrates exactly how it’s done.

Keep in mind that the embryos don’t go anywhere. Think of it like getting a mole from your body biopsied at a dermatologist’s office. You get the mole removed. It’s sent to the pathologist for testing, and you go home and wait for the results. You don’t physically go anywhere. The cells do. The same is true for your embryos. They will be chilling in the tank, frozen, waiting to go home on your transfer day.

Who should consider PGT, and when?

If you know me, then you can guess what I’ll say next. Everyone should consider it. I want patients to be fully informed about their options. I sit down with my patients and talk to them about all of the ways we can do IVF. I want them to be aware of their options.

There are reasons why doing PGT can give you a higher chance of pregnancy. That said, not everyone should do it. If your embryo is poor quality but strong enough to turn into a healthy pregnancy, I ask my patients to reconsider potentially stressing the embryo. Not everyone has to do it. If you don’t want to that’s okay too.

Here are times to consider it:

If you want to do embryo banking and have embryos for the future. This allows you to know which embryo to choose when you’re ready for your next pregnancy.
When you thaw eggs and want to use them then you can test them then too. It’s important to be discuss genetic testing of thawed eggs used to create embryos when you’re ready to use them. Be sure to read my tips here.
The same is if you’re using a surrogate. You want to make sure that the embryo you’re using has normal chromosomes based on testing. However, keep in mind that transfers and implantations of normal embryos can still result in loss. This is not an absolute guarantee like I wish that it was.
If you’re using previously frozen embryos or donated embryos. You can do genetic testing on frozen embryos if your clinic gives you the all-clear. If the embryos are already hatched then I don’t think it’s a good idea to test them. If they are poor quality, I would also not test them. Talk to your doctor about the state of your embryos and if it would be safe to genetically test them before you do it.

Are there any risks with PGT?

Yes! I just mentioned it above. We want to make sure that testing the embryos doesn’t damage them.

If you have someone that has no idea what they’re doing and then they biopsy your embryos, damage can happen. If you’re not going to a top-notch lab with excellent embryologists then you are at risk for having your embryos damaged.
The other thing that we’ve learned about recently is that doing the biopsy of the shell of the embryo (trophectoderm) may be linked to an increased risk of pre-eclampsia. A condition that we see not uncommonly in women that are pregnant for the first time, pregnant with twins, and over the age of forty, or already have medical problems like diabetes or hypertension pre-pregnancy.
Patients that have already gone through IVF with genetic testing may want to consider staying on their aspirin (81 milligrams) through 36 weeks of pregnancy to prevent preeclampsia. There’s a lot of good data surrounding that recommendation.
The other risk is that you can be going through the process of PGT and your clinic and a genetic testing company may withhold valuable information. For example: Are your embryos mosaic? How is that defined by your doctor and the genetic testing company? Important for you to have answers to these questions before you start IVF.

What are the benefits of PGT?

It is not a crystal ball, but it’s the best that we have. When we’re using science we sometimes rely on it a lot or even too much. It doesn’t give us the 100% pregnancy rate that I wish it could. I wish there was a guarantee I could give people. When things don’t work out it’s heartbreaking. It’s tough dealing with human biology. Understanding the limitations helps set expectations.
It does seem to reduce the risk of miscarriage as chromosomal issues are thought to be the number one cause of miscarriage.
It can save you time and give you a better chance of getting pregnant. This is true for your first transfer and subsequent transfers. If you’re going back to your doctor to get pregnant for a second time you can more confidently transfer if you know all of the embryos you have frozen have been genetically tested and know which one will give you a better shot at leading to a healthy pregnancy.
Doing this testing can also reduce the risk of having a baby with severe issues.

Why would I want to consider PGT?

Here are the potential reasons that I encourage you to discuss with your doctor:

When you’re doing IVF for pregnancy now and for later (fertility preservation)
If you have a history of recurrent miscarriages
To rule out inherited diseases
Gender — if you’re interested in having a baby of a certain gender

My Pro Tips:

Find out who is going to perform your biopsy. How long have they been doing it? What are their qualifications? Just as you’d interview or research a surgeon for your child you want to do the same for who will biopsy your embryo.
Do you have options for genetic testing companies? There are different genetic testing companies. Not all are the same. Ask your doctor why they are recommending certain companies. Are they a shareholder in one of the companies? You want full transparency in it. I am not a shareholder in any of these companies. I use three that I think will give my patients the best results every time.
Will the testing company report mosaicism? You don’t want possibly normal embryos destroyed.
Will your clinic allow you to transfer mosaic embryos? Not all will allow mosaic embryo transfers (I do), but it’s important to know what your options are.
Realize that sometimes results may be indeterminate. It happens maybe twice a year out of about a thousand embryos biopsied for me. I always do a post IVF consult with my patients going through all of the testing results. Do the same thing in person. And if this happens to you: Talk to your doctor, the genetic counselor at the genetic testing company and the embryologist. See whether you should consider a re-biopsy or not. Every situation is different when it comes to this and there’s no “one size fits all” if this happens to you.
How will an abnormal embryo be treated? Ask the question before you go through your cycle to understand what the process is for discarding abnormal embryos. Understand: How is it done? When is it done? What do you need to do?
Get access to the genetic counselor’s information. Ask more questions if you have them. I give my patients all of the information that I have but I ask patients to also talk to a genetic counselor to hear the information again and in a different way.

In Summary

This is everything I would want to know if I was a patient considering PGT. Here again, are the questions to get answers to as a fertility patient. Please discuss these with your doctor.

What is PGT?
How is PGT done?
Who should consider PGT, and when?
Are there any risks with PGT?
What are the benefits of PGT?
Why would I want to consider PGT?

Thank you for reading this. I hope that everything you’re doing as you’re working toward your goal is going to be successful. I’m sending you all of my positive energy.

As always, please send me a note, email@eggwhisperer.com, if you have any further questions or you’d like to recommend a topic for a future show.

You can also catch more of me and topics like this through The Egg Whisperer Show. The episodes are live-streamed on YouTube, Facebook, and Twitter and on Wednesdays at 7 PM PST. Subscribe to the podcast too!