If you’ve done IVF with embryo genetic testing (PGT-A) you’ve probably gotten some embryos with abnormal results. Your doctor may have told you that these embryos aren’t recommended for transfer, but you may not have been given any more information than that.
A lot of blood, sweat, tears, (and meds!) went into the creation of those embryos, so it’s normal to want more information about them. We’ll walk you through what it means for an embryo to be chromosomally abnormal, and whether these embryos can lead to a pregnancy.
What is implantation?
Implantation is the process of an embryo getting cozy and burying itself within the uterine lining. Soon after, the pregnancy hormone, β-hCG can be detected causing a positive pregnancy test. Implantation is the very first stage of pregnancy.
Implantation is different from an embryo transfer. A transfer is the process of your doctor placing an embryo inside the uterine cavity in the hopes that implantation will happen, but unfortunately not all embryos that are transferred end up implanting into the uterus.
What are chromosomes and why are they important?
Chromosomes are the packages that contain all of our genes. Genes are the instructions for the human body, so you can think of chromosomes like the instruction books, each holding thousands of genes together. Most people have 46 chromosomes in total. A healthy egg has 23 chromosomes and a healthy sperm has 23 chromosomes too. When a healthy egg and sperm come together, they create an embryo with 46 chromosomes.
If an embryo has a chromosome that is missing, this means there are thousands of genes that it is missing and thousands of important instructions for its development that it doesn’t have. If an embryo has an extra chromosome, this means it has thousands of extra genes. This means it is getting a lot of instructions in the wrong “dose” (like when you put twice as much salt in your cake recipe) which isn’t good either.
What is a chromosomally abnormal embryo?
In order to know that an embryo is chromosomally abnormal, a genetic test called PGT-A needs to be done on the embryo before it is transferred. There are a few different ways that PGT-A can be done, but it usually involves removing 5-10 cells from the area of the embryo that would become the placenta. These cells are opened, the DNA is removed, and testing is performed to estimate the number of chromosomes that the embryo has.
There are a few different types of results that you can get from PGT-A including euploid (normal), aneuploid (abnormal), mosaic (intermediate), and no result (inconclusive). Some clinics refer to embryos with mosaic and inconclusive results as “abnormal” but in this article “abnormal” only refers to embryos with aneuploid results.
Aneuploid can mean that PGT-A detected an extra chromosome, missing chromosome, a whole set of chromosomes that are missing or extra, or just a piece of a chromosome that is missing or extra.
So, can chromosomally abnormal embryos implant?
Yes, chromosomally abnormal (aneuploid) embryos can implant. Depending on the specific chromosome abnormality, some might be more likely to implant than others. But remember, implantation is just the first step of pregnancy. Aneuploid embryos have a lot of genetic instructions that are incorrect. If implantation occurs with an aneuploid embryo, the pregnancy usually does not keep going beyond the first trimester. This means that if an abnormal embryo implants there is a high risk of miscarriage.
Some embryos with chromosome abnormalities can lead to the birth of babies with genetic conditions due to the extra or missing chromosome. For example, an embryo with an extra copy of chromosome 21 could lead to a baby with Down Syndrome.
Finally, it is important to remember that PGT-A is not 100% accurate, and some aneuploid results are more accurate than others. If you want a detailed understanding of your abnormal embryos, you should meet with a Certified Genetic Counselor who specializes in PGT-A so they can walk you through what types of abnormal embryos you have. This will help you understand the meaning of your specific genetic results.
