Embryo Grading and Procedure: A Detailed Overview


Embryo grading is a pivotal aspect of in-vitro fertilization (IVF) treatments. It aids embryologists and fertility specialists in determining the best embryos for transfer, thereby maximizing the chances of a successful pregnancy. Understanding this process can provide couples undergoing IVF with clarity and assurance as they navigate their fertility journey.

1) What is Embryo Grading?

Embryo grading refers to the assessment of the quality of embryos developed in an IVF lab. This qualitative analysis helps determine which embryos have the highest potential for implantation and growth after transfer to the uterus.

2) Why is it Important?

Not all embryos have the same potential to implant and develop into a healthy fetus. Grading allows specialists to select the embryos with the best developmental prospects, increasing the success rate of IVF cycles.

3) The Grading Procedure:

The grading process varies between clinics, and there’s no universal grading system. However, most systems consider the following factors:

Day 3 Grading (Cleavage Stage)

Cell Number: By Day 3 post-fertilization, a healthy embryo should ideally have around 6-8 cells.

Cell Symmetry: The cells, called blastomeres, should be approximately equal in size. Asymmetry can sometimes indicate developmental issues.

Fragmentation: This refers to the broken-off pieces of cells seen within the embryo. Less fragmentation is preferable, with no or minimal fragments being the ideal scenario.

Cellular Regularity: The alignment and shape of the cells also play a role in grading.

Day 5/6 Grading (Blastocyst Stage)

Expansion Grade: Blastocysts (Day 5/6 embryos) are graded based on their degree of expansion and hatching status. A fully expanded blastocyst has a better implantation potential.

Inner Cell Mass (ICM) Grading: The ICM gives rise to the fetus. Its grading is based on the number of cells and their cohesiveness.

Trophectoderm Grading: The trophectoderm contributes to the placenta. Like the ICM, its cells are evaluated for number and cohesiveness.

4) What Comes After Grading?

Based on the grading and the clinic’s protocol, the best embryos are selected for transfer. This could be immediately during the fresh IVF cycle or after freezing for a future frozen embryo transfer (FET).

5) Does Grading Guarantee Success?

While grading provides a useful guideline, it doesn’t guarantee implantation and pregnancy. Some embryos that appear perfect might not implant, while others with lower grades might lead to a successful pregnancy. The grading system offers an informed choice but isn’t definitive.


Embryo grading is an invaluable tool in the world of assisted reproductive techniques. By understanding the nuances of this procedure, couples can better appreciate the meticulous care and expertise that goes into every step of their IVF journey, bolstering hope and trust in the process.

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