Day 5 – 7


At this time, the embryo should show early cavitation (CAV) or has reached a Blastocyst. The normal time expectation for blastocyst formation is between 5 to 7 days after Fertilization. If the embryo doesn’t reach the blastocyst stage during this time period, it will be discarded.

Blastocyst Grading

This grade defines the progression of the blastocyst and the quantity and quality of the cells within it.

There are two types of cells in the blastocyst. One cell type forms the Inner Cell Mass (ICM). These cells will eventually grow into the fetus. The second cell type is the Trophectoderm Epithelium (TE), these cells will go on to make the placenta and surrounding structures.

PROGRESSION: Higher number means more advanced stage of the blastocyst.

Stage 1 Early Blastocyst

Stage 2 Blastocyst

Stage 3 Full Blastocyst

Stage 4 Expanded Blastocyst

Stage 5 Hatching Blastocyst

Stage 6 Completely Hatched Blastocyst


1. After your embryo becomes a blastocyst it has an increased possibility to implant over the previous embryo stages. The ICM and TE grades of A and B have a higher possibility of implantation than a grade C.

2. Anything less than CAV or MOR on day 5 is not expected to reach Blastocyst.