Embryos are assessed by their appearance under the microscope for the number of cells, the characteristic of cells and the presence or absence of fragmentation. Good quality embryos divide rapidly, have equal cells with clear cytoplasm, and have only few fragments. Some IVF clinics classify the embryos into grade one, two, three and four.
Grade one are the best quality embryos, these have a higher chance of implantation than those of grade 4. Research has shown that up to one third of embryos are genetically abnormal. There is no guarantee that a normal looking embryo will be genetically normal. How embryos attach and implant into the womb remains a mystery