Understanding Embryo Grading for Intended Parents


Once your embryos have been created your first question to the doctor may be, “How good do the embryos look?” The answer you receive is typically referred to as the embryo’s “grade.” For many intended parents, the answer might as well be delivered in a foreign language. IVF is likely very new to you, and being told that your embryos are a 2.5 may not do much to answer your original question.

Embryo grading is determined by several factors, the first being the day in which the grade is given. Grades are typically delivered on either day 3 or day 5 of growth. Because the degree to which the embryo has developed differs drastically from day 3 to day 5, the method for grading will differ as well.

Day 3 Grading

During this phase of development, the cells divide rapidly. A dividing cell, in this phase of development, is not a growing cell. All cells at this stage will be roughly the same size, but the number of divisions within the cell may vary greatly.

As the cells divide, occasionally some of the cytoplasm, the inside of the cell, will break off and form smaller “fragments” that do not contain a nuclei and are not considered a true “cell”. These fragments occur naturally and do not immediately suggest poor embryo quality.

Day 3 cells are graded based on the number of cell divisions visible relative to the number of fragments that are visible. Typically, doctors hope to see between 6-10 equally sized cells and an absence of fragments in an ideal day 3 embryo.

The grading scale will continue to look at cell divisions and fragmentations and assign a numerical grade between 1-4. Doctors expect embryos with a grade of 1-2.5 to have the most likely chance of continuing to develop into a day 5 blastocyst.

Day 5 Grading

Most doctors will wait to issue a grade until the embryo reaches the blastocyst stage on day 5 of development. While cells are continuing to divide, they are now also growing in volume. This means that they may outgrow their “shell” and begin to hatch in preparation for implantation into the uterine lining.

Another part of development on day 5 is that there are now two types of cells present. The inner cell mass (ICM) which will eventually turn into the fetus, and the Trophectoderm Epithelium (TE) which will eventually form necessary tissues needed for pregnancy, including the placenta. Doctors will be looking for both types of cells and judging their appearance when issuing a day 5 embryo grade. Other considerations include the fluid cavity between the two cell types and how much the embryo has expanded.

Once they’ve finished evaluating the embryo, doctors will issue a letter grade to the blastocyst. Most doctors will issue a grade for each type of cell, resulting in a two letter grade. Other doctors will also give a third letter grade to correspond with the growth. As a result, the best quality day five embryo will receive a grade of “AAA” or “AA.”

Doctors then consider the grading of each component of the cell when deciding if they believe the embryo is likely to continue growing and result in a positive pregnancy. The grading system at this stage can be quite subjective and is therefore not a guarantee. Even the best graded embryos may fail to implant and grow while, embryos with a lower grade may occasionally develop into a healthy pregnancy. It is important to remember that grading is just a tool and not a promise of success.

If you find that you still have additional questions on embryo grading or how to understand the grading system, don’t be afraid to speak with your case specialist or IVF doctor.

Kim Bergman, PhD, a licensed psychologist of 26 years, has specialized in the area of gay and lesbian parenting, parenting by choice and third party assisted reproduction for over two decades. Dr. Bergman has created a comprehensive psychological screening, support and monitoring process for intended parents, surrogates and donors. She is the co-owner of Growing Generations and is a member of the American Society for Reproductive Medicine, the American Psychological Association, the Los Angeles County Psychological Association, the Lesbian and Gay Psychotherapy Association, and the Gay and Lesbian Medical Association. She is on the national Emeritus board of the Family Equality Council. Dr. Bergman writes, teaches and speaks extensively on parenting by choice. Along with co-authors, she published “Gay Men Who Become Fathers via Surrogacy: The Transition to Parenthood” (Journal of GLBT Family Studies, April 2010). Dr. Bergman’s is the author of the book, Your Future Family: The Essential Guide to Assisted Reproduction (Conari Press 2019) as well as the children's book You Began as a Wish (Independent Press 2019). Dr. Bergman created her own family using third party assisted reproduction and she lives with her wife of 35 years. She has two adult daughters.