Embryo grading takes place on days three and five after fertilization. Knowing how embryo grading and success rates work is an important part of your IVF journey.
Understanding embryo grading and success rates can give you an insight into how the best embryos are chosen for transfer. Although embryo grading isn’t the only determining factor for a successful transfer, transferring the best embryos increases the chances of a successful pregnancy.
High-grade embryos often have a good chance of implantation, but lower-grade embryos can also result in healthy pregnancies.
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Embryo Grading and Success Rates
After your embryos are created, part of the in-vitro fertilization (IVF) process for your medical team involves watching the growth of the embryos. They will decide which embryo is most likely to successfully result in a pregnancy.
While there are additional factors that go into a pregnancy, embryos are graded, and eventually selected, based on their quality.
Does Embryo Grading Matter?
Yes, embryo grading matters. It’s a procedure and one of the tools used by medical professionals to not only evaluate but select which embryos would be best to transfer. Some studies show that higher-graded embryos are more likely to result in a pregnancy as a result of IVF.
Day 3 Embryo Grading and Success Rates
Day three embryo quality is graded on:
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Number of cells
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Appearance of cells
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Degree of fragmentation
After looking at the number and appearance of cells, number or letter grades (depending on your clinic’s scale) from 1-4 or A-D are then assigned based on the degree of fragmentation, with 1 or A being the best.
Embryo grading scales for day three embryos can look different depending on the professionals you work with, some only use letters and a shorter range of A-C and some use a number scale that goes from 1-5.
Cells are similar, no fragmentation is seen Cells are similar, fragmentation is minimal (0-10%) Cells are mostly similar, fragmentation is moderate (11-25%) Cells are not similar, fragmentation is moderate to severe (26-50%)Example of a Day 3 Embryo Grading Scale
Here’s what day 3 embryo grading and success can look like:
Grade Description Live Birth Rate A Cells are similar, no fragmentation is seen 40-50% B Cells are similar, fragmentation is minimal (0-10%) 30-40% C Cells are mostly similar, fragmentation is moderate (11-25%) 15-25%
What Is the Most Successful Embryo Grade?
Embryos graded three or higher, indicating a fully developed blastocyst at minimum, with an AA letter grade have the highest chance of pregnancy. These grades indicate higher implantation and success rates but lower graded embryos can still lead to healthy pregnancies.
Day 5 Embryo Grading and Success Rates
Day five embryo quality is graded on:
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Blastocyst expansion
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Appearance of the inner cell mass (ICM)
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Appearance of the trophectoderm epithelium (TE)
In addition to the continued growth of the embryo that’s being graded, the appearance of the ICM and TE are crucial for a healthy, successful pregnancy.
For day five embryos, the Gardner system is commonly used to grade them.
Blastocyst development stage: Expansion and hatching status ICM quality TE qualityGardner Blastocyst Grading System
The components of the day 5 embryo grade listed above are ordered with 6, A and A being the highest points of the scale, respectively.
Embryo transfers with an “excellent” grade, greater than 3aa, at this stage have a pregnancy rate of 65%. It drops to 50% if the grade is average, like a grade of 2ab or 4ca, and even further to 33% if the blastocyst is graded as poor, such as 2bb or 3bc.
Poor quality embryo grading and success rates do go together as a lower graded embryos are less likely to be successful.
The grading scale used for embryos gives you an indication of the potential for a pregnancy. Embryos graded as “excellent”, no matter what grading scale is used, often result in higher pregnancy and live birth rates than embryos that receive “good” or “average” grades.
Embryo Grade Pregnancy Rate Live Birth Rate 3AA, 4AA, 5AA 65% 50% 3AB, 4AB, 5AB 55% 40% 3BB, 4BB, 5BB 30% 20% 4BC, 5BC, 6BC 10% 5%
Is 4AA or 5AA Better?
Both 4AA and 5AA embryos are considered excellent when it comes to the Gardner grading system. Any embryo graded 3AA or above had clinical pregnancy rates of 65% with the difference between the numbers being an expanded blastocyst vs. a hatching blastocyst.
Whether you need help with finding a reputable fertility clinic to create and grade your embryos or preparing for IVF or surrogacy, we’re here for you. Fill out our online contact form to get the support you deserve.