A Game of Telephone: Common Misconceptions About PGS

By Hayley Ladjack — August 16, 2018

4 min read

As a child, one of my favorite games to play was telephone. If you’ve played before, you’ll know that the basis of the game is to line up and listen to what the person on your left whispers in your ear, before passing it on to someone else on your right. Usually, a phrase is repeated poorly often enough that it sounds completely different when it reaches the last person, with hilarity ensuing as a result. Imagine “My neighbor Bob parked his car down the street” turning into “Mandy’s brother Caleb has smelly feet”.

Unfortunately, there’s nothing funny about the game of telephone that you experience as a patient looking for answers to your questions about IVF. Since there is so much to cover in every doctor’s visit, it’s (understandably!) impossible to retain and comprehend everything the first time around. Many doctors will actually recommend that you seek out information on your own to aid your understanding of the fertility treatment process and accompanying procedures like preimplantation genetic screening, or PGS, but there’s a lot of misinformation out there on the web.

If your doctor told you one thing, and after googling PGS you’ve somehow ended up with vastly different information, you might have some misconceptions about how the process really works. To help you avoid the vicious cycle of telephone between the internet, you, and your care team, I’ve explained the PGS procedure and combatted some of the most common PGS misconceptions found on the net.

The basics of PGS

Preimplantation genetic screening (PGS) is a genetic test performed on IVF embryos that gives information about embryos’ genetic health. The test looks specifically at the chromosomes contained within the cells of these embryos to be sure that there are 23 pairs of chromosomes in each cell. This is important to IVF patients because missing or extra chromosomes in embryos can cause failed implantation, miscarriage, or a child born with a genetic disease. With this type of screening added to your IVF cycle, your care team will have extra information that they can review with you before transfer, which helps you choose the embryo(s) with the best shot at a successful pregnancy.

Misconception #1: “I don’t have any genetic diseases in my family, so I don’t need to do genetic testing with IVF.”

If you don’t have any family members afflicted with genetic diseases and you already know that you and your partner are not carriers, it makes sense that you may not be worried at all about genetic testing. However, genetic abnormalities can arise in various ways; they can be inherited but they can also happen spontaneously. Therefore, every embryo (conceived naturally, or developed in a lab) has the potential for abnormalities.

One common type of genetic abnormality is called aneuploidy; this occurs when cells have extra or missing chromosomes. Even without any family history, everyone is at risk for creating aneuploid embryos. This risk exists for women of all ages, but increases as a woman gets older. Aneuploid embryos typically result in a very early loss (often before a woman even knows she is pregnant), a miscarriage, or the birth of a child with a chromosomal condition (e.g. Down’s syndrome). In fact, it is estimated that 60% of all miscarriages in the first trimester can be attributed to aneuploidy (Stanford Medicine). Fortunately, PGS can be helpful in identifying aneuploidy before you’re even pregnant, which gives you the option to choose the healthiest embryo for transfer, and a higher chance of successfully delivering a healthy baby.  

Misconception #2: “My doctor said that my embryos look good so I don’t need to do PGS.”

If your doctor told you that your embryos look great, that is a plus when considering whether or not to transfer them. However, the idea that high-grade embryos don’t need to be tested is antiquated–an embryo of a high grade or quality simply means that they have grown to be the correct size, shape, and consistency. This does not give clues to the overall genetic health of the embryo, which has a huge impact on its potential success for implantation and forming a healthy pregnancy. Even if your doctor tells you that your embryos are high quality or have good morphology, it is still possible that they could be aneuploid embryos, which can result in failed implantation, miscarriage, or a child born with a chromosomal disease.

Misconception #3: “I’ve heard that sometimes abnormal PGS embryos can lead to successful pregnancies.”

During PGS, doctors work with patients to help them prioritize transfer of their (genetically) healthiest embryos, which means a higher chance of pregnancy and a lower chance of miscarriage. Following your embryos’ PGS screening, your doctor will help you go through your results, which may include embryos that are euploid, aneuploid, or mosaic. Euploid (normal) embryos have the best chance of implantation and pregnancy success, while doctors typically recommend that aneuploid (abnormal) embryos are not transferred. However, mosaic embryos are a little trickier.

Mosaic embryos contain both normal and abnormal cells, and these embryos are thought to have an intermediate chance at producing a healthy pregnancy. Though mosaicism has always existed, it has only become detectable by PGS technology within the last four years. With this in mind, if you’ve heard from those who claim “abnormal” embryos led to the birth of a healthy baby, they are most likely speaking about mosaic embryos that were classified as aneuploid by older technology. While mosaicism research is still ongoing, what we know now is that these embryos implant less and miscarry more than euploid embryos but can, in some cases, still lead to healthy live birth. Not all PGS laboratories report mosaicism, so it’s important to ask your doctor what laboratory they are planning to use and what reporting options you have.

Misconception #4: “My embryos might get lost during transit to the testing facility or part of the PGS procedure could harm them.”

When many patients decide to pursue PGS, they might think that this will require having their embryos shipped to a different facility for testing, and this can sound like a scary thought, after you’ve gone through so much just to get them safely to this stage. However, the PGS procedure is actually performed on just a small sample of about 5-10 cells collected from your whole embryo (made up of 100-200 cells) during a procedure called a biopsy. While a testing facility will receive this sample for testing, your embryo will not travel at all, but will instead be flash-frozen, and remain in the care of your IVF center. Be that as it may, a patient’s next concern is often for the embryos’ safety during the biopsy.

Biopsies are performed by highly trained and skilled individuals, called embryologists, when your embryos are about 5 days old. During biopsy, an embryologist will use advanced tools to carefully remove several cells from the part of the embryo (called the trophectoderm) that will go on to form the placenta, while the part that will go on to form the baby (the inner cell mass) remains untouched. Patients can take comfort in knowing that with a skilled embryologist, the risk of damaging an embryo during biopsy is now very low.

Don’t let your phone lines get crossed

The next time you’re surfing the net and just so happen to stumble on a post or forum offering medical advice, remember to do your research and not take everything you read or watch at face value. As easy as it might be to trust information from your favorite blogger, your best bet is to scout for more reliable sources, and always turn back to your team of healthcare professionals. Rather than being subject to a game of telephone, you might even want to consider picking up yours and reaching out to a licensed genetic counselor. That said, if you’re still set on looking to the web for answers, we recommend this PGS video to help get you started. Happy viewing!

References:

http://www.stanfordchildrens.org/en/topic/default?id=how-chromosome-abnormalities-happen-meiosis-mitosis-maternal-age-environment-90-P02126