Generally, blastocysts are still usable if they are naturally wrinkled. A blastocyst is a fertilized egg that divides in a series of divisions to create a hollow sphere surrounded by a single layer of cells. It usually develops around 5 days after egg retrieval and a sac cavity begins to form between the cells. However, when observing the blastocyst, part of the cavity may collapse, a condition known as blastocyst crumpling. When the blastocyst is crumpled, the trophoblast layer and inner cell mass are crumpled together, making it difficult to accurately assess the quality of the blastocyst, which can be reevaluated by waiting for an hour for the cells to expand. Therefore, blastocyst crumpling is just a normal part of blastocyst development and is generally usable. Most blastocysts in the clinic will undergo multiple natural crumpling and reexpansion of the blastocyst from early development to full hatching. Therefore, as long as the blastocyst passes the evaluation, it can be used normally.