How does an embryo get graded?

What Is Embryo Grading?

“Embryo grading is the process where embryologists examine how the embryo looks as it develops in the IVF laboratory,” explains Professor Gardner. This assessment provides a guide to prioritize embryos for transfer, freezing, or further monitoring. While not a guarantee of success, grading helps identify embryos with the highest potential to lead to a healthy pregnancy.

Embryo grading typically takes place five days after fertilization, when the embryo reaches the blastocyst stage.

How Are Embryos Graded?

At the blastocyst stage, embryologists evaluate two key parts of the embryo:

1. Inner Cell Mass (ICM): “These are the cells that will form the baby,” says Professor Gardner.
2. Trophectoderm: “This outer layer of cells is responsible for implanting the embryo into the uterine lining.”

Each part is graded:

• A: Many well-organised cells.
• B: Several cells with slightly less organisation.
• C: Few cells or a disorganised structure.

Embryologists also score how much the blastocyst has expanded, assigning a number from 1 to 6 (higher numbers indicate healthier embryos).

“The overall grade combines the numeric expansion score with the two letters for cell quality,” explains Professor Gardner. For instance, an embryo graded 4AA has expanded well and has excellent inner and outer cells.

“This system, known as the ‘Gardner Grade,’ is the global standard for human embryo grading,” he adds.

What Do Embryo Grades Mean for Success?

“The Gardner Grade is highly predictive of embryo transfer outcomes,” says Professor Gardner. In general, higher grades indicate a greater chance of implantation and pregnancy.

For couples like Ilina and Nick, receiving a highly graded embryo after years of trying was a significant moment. “A high-grade embryo offers hope, but grading is only part of the picture,” Professor Gardner notes. Other factors, such as the genetic health of the embryo and the uterine environment, also play crucial roles.

Are Higher-Graded Embryos Always the Best Choice?

“In most cases, the higher the grade, the better the chance of success,” says Professor Gardner. However, there are exceptions. For instance:

• Chromosomal Abnormalities: “Even a high-grade blastocyst may have an abnormal number of chromosomes, particularly in women over 37,” he explains.
• Genetic Testing Results: Advanced genetic testing can identify embryos with the correct number of chromosomes, which increases the likelihood of success.

How to Choose an Embryo for Transfer

If you have embryos with varying grades, the highest-graded one is usually selected first. “Our experienced scientists use a proven ranking system to prioritize embryos with the best chance of implanting,” says Professor Gardner.

Additionally, technologies like artificial intelligence (e.g., iDA) can refine the selection process. “When we have two or more embryos with the same grade, AI assists in ranking them for transfer,” he explains.

Other Factors That Influence Success

While embryo grading is important, other factors also play a role in IVF success:

• Genetic Testing: “For patients over 37, a biopsy of the trophectoderm can determine the number of chromosomes, identifying chromosomally normal embryos,” says Professor Gardner.
• Uterine Environment: “A healthy uterine lining and balanced hormones are essential for implantation,” he adds.

Advice for Couples with Lower-Grade Embryos

If your embryos have lower grades, it’s natural to feel anxious. Professor Gardner reassures couples that even lower-grade embryos, like those graded CC, still have a chance of leading to a healthy pregnancy, albeit with reduced odds.

“When a blastocyst scores a low grade, it’s important to discuss transfer options with your physician,” he advises.

While a high grade often brings hope, it’s just one piece of the puzzle. As Professor Gardner says, “Embryo grading is not the end of the story—it’s a guide we use to assist us in helping couples move closer to their goal of parenthood.”

To learn more about embryo grading, don't hesitate to reach out to talk to one of our fertility specialists on 1800 111 483.