The Art Of Selecting The Right Embryo

Ashleigh Storr (BSc, PGDip, PhD) one of our very own embryologists, recently presented at the annual Fertility Society of Australia (FSA) conference in Melbourne about selecting embryos for transfer in today’s IVF laboratory.


In order to achieve the goal of taking home a healthy baby for our patients, the IVF stimulation process has been refined over the years to enable the collection of multiple eggs. This means we will hopefully have multiple embryos in our laboratory incubators that are growing to day 5 – also known as the blastocyst stage (see image above).

The health benefits to both mother and child of transferring just one blastocyst at a time (single blastocyst transfer) into the uterus are now very well documented and recognised around the world. However, this has placed more importance on the ability of the embryologist to select a single blastocyst with the highest chance of achieving a pregnancy.

Ashleigh-FSA-Crop.jpgGrowing our embryos to day 5 is important for embryo selection in the laboratory as it provides a form of natural selection. This natural selection isn’t 100% guaranteed, but we know that many embryos are genetically abnormal and therefore may not be able to grow and develop to reach day 5. These embryos will sometimes arrest at an earlier stage of development (for example, Day 1, 2, 3 or 4) and will never be selected for transfer. In fact, the percentage of genetically abnormal embryos can actually be quite high, even at age 30 (around 25%).

Allowing embryos to grow to day 5 means, in many cases, we will still have more than one good quality blastocyst to choose from. Given that the embryologist only wants to choose one for transfer, an important question remains: how do embryologists choose the one blastocyst that is most likely going to result in a pregnancy?

Ultimately, one of the major determining factors for pregnancy achievement after IVF is embryo quality, and in order to select the best blastocyst for transfer, embryologists use grading systems. These grading systems allow embryologists to rank blastocysts based on the quality of developing structures we can only see under a microscope. By doing so, embryologists are able to make an informed decision on which blastocyst has the highest chance of implanting and resulting in an ongoing pregnancy.

More recently, preimplantation genetic testing (PGT) as well as other novel technologies such as artificial intelligence have become available to IVF laboratories and can be used in conjunction with blastocyst grading. Introducing these new technologies will benefit patients by helping embryologists select the best blastocyst for transfer and increase the chances of implantation and taking a baby home. It truly is an exciting time for patients undergoing IVF!

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