What are the recent developments in implantation? (Part Two: Embryo grading)

Posted by & filed under IVF, Tests, The Basics.

This post is part one of a series where we will discuss how embryos, the uterus and overall health impact implantation.


We judge embryo quality in three ways: the number of embryos present, embryo grading, and PGS. In this post, we’ll talk about embryo grading.

Stretched over the first 96 hours of development, we remove embryos from the incubator for about two minutes to look at the embryo and assess its capacity for ongoing development.

Two minutes doesn’t seem like a lot of time, but it’s enough. The gases and temperatures outside of the incubator are inappropriate for embryo development, so limiting their exposure to a non-incubator environment is important. We grow embryos to the blastocyst stage. If the embryo has survived that long, there is a greater likelihood it will continue to develop. This increases your chances for pregnancy.

By day one of development, we should see cells that have two “balls” of DNA collected, from the egg and from the sperm. If there is only one or there are three, or even zero, the embryo is not developing well.

By day three, the embryo should have six, seven, or eight cells.

By day five, the size of the blastocyst is measured instead of the number of cells. A number (usually 1 through 6) represents the size and letters (A through D) make note of the inner cell mass and what will make the placenta (trophectoderm) in the future.

These grading systems are okay, but not ideal. Not all high-quality embryos will implant, and not all low-quality embryos will fail.

To improve our information, there are newer techniques for grading embryos. We now have the ability to watch embryos grow in the incubator for the full 96 hours, their development captured on video throughout. This removes the need to take the embryos out of the incubator, and we collect a lot more data.

The current challenge is to know what exactly to do with that data. Researchers and scientists are working to generate new algorithms to help identify which embryos are most likely to continue to grow. Different companies are working to provide solutions to fertility clinics. The EEVA test, in partnership with Auxogyn/EMD Serono is one example.


Note: Embryos are just one element in implantation. Implantation challenges can be related to embryos, the uterus and overall health. We’ll have another post shortly on how the uterus, its shape and lining, may impact odds for implantation.

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