The embryos at this stage are often referred to by the number of cells they contain. The day 6 embryo is forms what is commonly known as a blastocyst. This is the stage when the day 6 embryo transfers are done. As you can see by the image, the cells have undergone several divisions. Following several more cell divisions the group of cells undergo hatching.
Hatching is when the embryo leaves the zona pellucida and prepares for implantation.
Assisted hatching involves making a small defect in the zona pellucida to facillitate the hatching process. The embryo is the area on the right. Please do not submit individual or personal questions that pertain to patient care. Duke University Reproductive Endocrinology and Infertility.