What the Heck is an Embryo Mitoscore?

The mitochondrial DNA test is a new scoring mechanism meant to help aid the selection of embryos that have the highest chances of implantation. In this guide, we’ll talk about what the mitoscore can, and can’t, tell you.

By Halle Tecco, MBA, MPH

You may have recently gotten an embryo genetic report from your IVF clinic including something called a mitoscore. This data was not around during my first two rounds of IVF, but I did get the report for my third and fourth rounds in 2020. This is a relatively new scoring mechanism, and in this article, we’ll dive into what the heck it means.

What is a mitoscore?

A mitoscore of an embryo is a number created during mitochondrial DNA testing. Mitochondria are structures within cells that play an essential role in energy production. They have their own DNA, known as mitochondrial DNA or mtDNA. The number of mtDNA of a chromosomally normal embryo is related to a state of energy, which affects the ability of the embryo to implant in the uterus. Mitochondrial function, mtDNA gene expression, and energy are required to undergo necessary cellular divisions to form a high quality embryo. Some early studies have shown that higher mtDNA content in an embryo indicates a low level of energy, and thus, a lower chance of implantation. 

The mitochondrial score, or mitoscore, is a value that represents the normalized mitochondrial DNA content in an embryo. The predictive value of this test is still considered experimental. 

Early research shows an embryo’s mitoscore may predict the implantation rate

If you are so lucky to have multiple genetically normal embryos to choose from, your doctor may use the mitoscore (along with information about morphology and PGT-A results) to help choose the embryo that has the greatest chance for implantation. Keep in mind that this is an emerging tool. As more data is collected, the score will continue to improve in its ability to predict implantation rate. 

What is a good mitoscore? Lower is better

One study showed that mitoscore data predicts pregnancy success and confirmed that lower mitoscore values were better. In this study, embryos with mitoscore values <25 had a significantly improved pregnancy rate at 85.2%.

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Another study of 270 embryos broke down the mitoscore between Day 3 embryos and Day 5 embryos. This study concluded that an increased amount of mtDNA, as indicated by a higher mitoscore, is related to lower implantation rates. 

Implantation rate by mitoscore

Because the mitoscore is a newer tool, it is being used to complement (not replace) other methods, like embryo morphology and PGT-A testing, of predicting success. There are myriad other parameters impacting the implantation and live birth rate, including BMI, age, day of embryo biopsy (Day 5 vs. Day 6), and history of miscarriage. 

How do I get a mitochondrial DNA testing for my embryos?

The mitoscore uses the same sample used for PGT-A. So if you are doing a frozen round of IVF and your clinic is ordering genetic testing of the embryos, it may be possible to get a mitoscore too. Here are the companies currently offering mitochondrial DNA testing: 

• MitoSure by Progensis
• Mitograde by Reprogenetics
• MitoScore by Igenomix

Take-aways

• Mitochondrial DNA testing (and the resulting mitoscore) is an emerging way to help identify an embryo’s energy production.
• Early research indicates that the mitoscore may be predictive of implantation rates.
• One study showed that embryos with mitoscore values <25 had a pregnancy rate of 85.2%. Another study showed that mitoscores under 18.19 had an 81% chance of implantation. 
• Ask your REI or embryologist if you have any questions or concerns about your embryos’ mitoscores. 

IVF can be an amazing way to grow a family. I know—I would not be a mother today without IVF. But it also comes with emotional ups and downs. If you want to learn more about fertility treatments, sign up for my personal IVF newsletter. 💌

Featured Image by Irina Iriser