Genetic testing of embryos is an important step in the IVF process for intended parents. It ensures that the embryos with the best chance of developing into a pregnancy are selected for embryo transfer to your surrogate.
By knowing the types of embryos and their success rates, you can better understand your PGT results and feel more confident in your IVF process for surrogacy.
If you have any questions about how the medical process works in surrogacy, check out this article. Have you already created your embryos? Contact us today to begin your surrogacy journey.
What is Preimplantation Genetic Testing? [2 Common Types]
In the context of assisted reproductive technology, genetic testing of embryos helps detect chromosomal anomalies and specific genetic disorders before implantation.
This ensures the selection of the healthiest embryos, increasing the chances of a successful pregnancy and reducing the risk of genetic diseases.
There are two primary types of preimplantation genetic testing (PGT):
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PGT-A (Preimplantation Genetic Testing for Aneuploidy): Formerly known as preimplantation genetic screening (PGS), PGT-A examines the number of chromosomes in an embryo. This helps identify embryos with the correct number of chromosomes (euploid) and those with an abnormal number (aneuploid).
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PGT-M (Preimplantation Genetic Testing for Monogenic Disorders): This type of testing is used to identify specific genetic mutations associated with single-gene disorders, often used when there is a known family history of inherited conditions.
Success Rates of Genetically Tested Embryos [PGT-A]
Success Rates for Aneuploid Embryos (Abnormal Embryos)
An aneuploid embryo has an abnormal number of chromosomes, either missing or having extra chromosomes. Factors influencing aneuploidy include maternal age, genetic mutations and environmental factors. Common disorders resulting from aneuploidy include Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), and Patau syndrome (trisomy 13).
The aneuploid embryo transfer success rates are significant in terms of implantation and live birth. Transferring aneuploid embryos often leads to failed implantation, miscarriage or birth defects.
Success Rates for Euploid Embryos (Normal Embryos)
A euploid embryo has the correct number of chromosomes, 46 (23 pairs) in humans. Maternal age, overall health and genetic background can influence the likelihood of producing euploid embryos. Euploid embryo success rate is higher for implantation and live birth. They are generally selected for transfer to increase the chances of a healthy pregnancy.
Reporting has consistently shown that pregnancy rates from transfers of euploid embryos are around 70%. Within that, implantation can still fail in close to 30% of transfer. A variety of factors can impact success, including things like the age of the embryo (day 5 embryos have been shown in some studies to have a higher euploid embryo success rate) and the age of the carrier.
Success Rates for Mosaic Embryos
Mosaic embryos contain a mix of euploid and aneuploid cells. This means some cells have the correct number of chromosomes, while others do not. The mosaic embryo success rate fall between those of euploid and aneuploid embryos.
While they can lead to healthy pregnancies, the outcomes are less predictable and there's a higher risk of complications. One study that observed 1,000 mosaic embryo transfers found an implantation rate of 46.5% and an ongoing pregnancy rate of 37%.
The percent aneuploidy within a mosaic embryo can also have an impact on the mosaic embryo success rate. This percent refers to the amount of abnormal cells within the mosaic embryo.
The same study of 1,000 mosaic embryo transfers found that mosaic embryos with less than 50% aneuploidy had higher success rates than those with a greater number of abnormal cells.
PGT-M
PGT-M is utilized to identify embryos that carry specific genetic mutations responsible for single-gene disorders. This testing is beneficial for couples with a known family history of genetic conditions.
A genetic condition that affects protein in the body’s cells, tissues and glands that make mucus and sweat. Also known as Huntington’s chorea, this is a neurodegenerative disease that causes nerve cells in the brain to breakdown and die. A lifelong, inherited blood disorder that causes red blood cells to become rigid and sickle shaped. A rare, inherited genetic disorder that causes nerve cell death in the brain and spinal cord typically caused by a mutation in the enzyme hex-osaminidase A. Common Disorders Covered by PGT-M Embryo Testing
The success rates of embryos tested with PGT-M largely depend on the genetic condition being tested and the quality of the embryo. However, using PGT-M increases the likelihood of a healthy pregnancy by ensuring the selected embryos do not carry the specific genetic disorders.
By understanding the types of embryos and embryo testing success rates, you’ll be able to embark on your journey to parenthood knowing how to maximize the chances of successful and healthy pregnancies. If your embryos have been created and you’ve completed PGT (if desired), you’re ready for the surrogacy process contact us online now.