Under the Microscope: Maximizing embryo freezing survival

The above embryo is being collapsed manually using laser assisted hatching.

We do this to remove the fluid inside the cavity and to reduce the size of them embryo. The reason for this is to decrease the chances of ice crystal formation and to increase survival of the embryo.

You can see the start-to-finish appearance of the embryo is completely different and many patients who have had an FET will ask why their blastocysts look differently than the ones generally portrayed in media. This is because you are seeing the embryo in its compacted shape - it takes a few hours of re-expansion for the embryo to return back to its original size/shape.

Collapsing blastocysts is standard practice in our lab because we find that it improves survival rate. If too much fluid is left inside, there is a higher likelihood of ice forming. Ice > crystals > cell death > not good news!