How to grade a blastocyst?

22.jpgThe EQC test will present you several possible answers for the various characteristics of a blastocyst. You can make only one choice. Although you may not be used to grade the blastocysts in your day-to-day activity, grading is a convienient way of communicating blastocyst characteristics both to colleagues and medical staff. In our view, it this is an important parameter to monitor in an External Quality Control scheme.


The blastocoele is an fluid filled intercellular cavity which increases its volume during blastocyst expansion. This process eventually leads to hatching, allowing thus the blastocyst to enter in contact with the uterine endometrium and to implant.

Parameters              Morphological aspect
Small the volume of the blastocoele is less than 50% of the total volume
Medium the volume of the blastocoele is greater than 50% of the total volume
Large the blastocoele occupies the whole volume inside the zona pellucida and has started expansion, leading to a thining of the ZP

Inner cell mass

The inner cell mass is a mass of cells inside the blastocoele which will eventually give rise to the definitive structures of the fetus. The number of cells in the ICM and the degree of compaction of these cells changes during blastocyst development.

Parameters Morphological aspect
Many compacted cells the ICM contains manny small compacted cells.
Few poorly compatec the cells in the ICM are still separated and porrly compated
Few cells the ICM contains either few cells or is barely/not visible


Also known as trophoblast, the trophectoderm is a single layer of cells tightly associated cell at the periphery of the blastocyst.

Parameters           Morphological aspect
Many cells forming a tight epithelium the trophectoderm appears clearly made of many small cells tightly attached and forming a single layer epithelium
Few poorly attached cells the trophectoderm is made of identifiable cells
Very few cells the trophectoderm contains few cells