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Euploid Embryo Vs Aneuploid Embryo

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The road toward parenthood can be filled with a mix of challenges and hope. But today, Assisted Reproductive Technology (ART) offers new avenues toward making your baby dreams a reality.

At TRIO, we strive to help individuals and couples use ART to create or expand their families. When undergoing fertility treatments, your fertility doctor will discuss with you the process of Preimplantation Genetic Testing (PGT-A). This embryo genetic testing examines the embryo at a chromosomal level. It determines whether the embryo has abnormal or normal cells — or a mix of the two.

From these tests, the embryo can be categorized as euploid, aneuploid, or mosaic. So, what do these terms mean exactly? What should you know about euploid and aneuploid embryos? In this article, we explore these answers and more.

What is an Euploid Embryo?

An euploid embryo is an embryo with the correct number of 46 chromosomes. In other words, this is a “normal” embryo. As a result, this embryo has a good chance of healthy development and growth.

What is an Aneuploid Embryo?

An aneuploid embryo is an embryo with an abnormal number of chromosomes. This means it either has extra or missing chromosomes. So, what does this mean exactly?

The reason for genetic testing is to determine if the embryo is abnormal. When PGT testing indicates an aneuploid embryo, we don’t perform an embryo transfer. This is because this type of embryo is more likely to lead to:

  • Failed implantation
  • Miscarriage
  • Developmental problems
  • Genetic disorders
  • Other physical or intellectual challenges

The most common type of aneuploid embryo disorder is Trisomy 21, or Down Syndrome. This syndrome happens when the embryo has an extra chromosome 21.

What are the Differences?

The main difference between an aneuploid and an euploid embryo is the number of chromosomes.

A normal, or euploid, embryo contains 46 chromosomes — or 23 pairs, with each pair inheriting a chromosome from the biological mother and father. Yet, an aneuploid embryo may have more or fewer chromosomes.

What are Mosaic Embryos?

Mosaic embryos contain both normal and abnormal cells. Surprisingly, 15% of all embryos are mosaics. However, these embryos tend to fall into a grey area. They can further range from low to high level mosaic embryos. This all depends on the percentage of normal versus abnormal cells.

Mosaic embryo transfer tends to be a controversial area in the world of ART. Transfer of low level mosaic embryos is generally safe. Transfer of high level mosaic embryos often lead to miscarriages, low implantation, and so your doctor and genetics counselor will advise you accordingly.

At TRIO, we strive to stay up-to-date on all the latest research regarding mosaic embryos. In this way, we can ensure all of our patients are informed every step of the way.

For any additional questions, reach out to a TRIO doctor today. Our team works with you to determine the best step forward specific to you and your situation.


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