The following day after eggs have been inseminated or injected with a single sperm (ICSI), they are examined for signs that the process of fertilization is underway. At this stage, normal development is evident by the still single cell having 2 nuclei; this stage is called a zygote. Two days after insemination or ICSI, normal embryos have divided into about 4 cells. Three days after insemination or ICSI, normally developing embryos contain about 8 cells. Five days after insemination or ICSI, normally developing embryos have developed to the blastocyst stage, which is typified by an embryo that now has 80 or more cells, an inner fluid-filled cavity, and a small cluster of cells called the inner cell mass.
It is important to note that since many eggs and embryos are abnormal, it is expected that not all eggs will fertilize and not all embryos will divide at a normal rate. The chance that a developing embryo will produce a pregnancy is related to whether its development in the lab is normal, but this correlation is not perfect. This means that not all embryos developing at the normal rate are in fact also genetically normal, and not all poorly developing embryos are genetically abnormal. Nonetheless, their visual appearance is the most common and useful guide in the selection of the best embryo(s) for transfer.
The Hanabusa Embryologist Team gives special care throughout every step of a couple’s journey to parenthood. Just as our approach to IVF focuses on retrieving the best quality eggs and combining them with the healthiest sperm, we similarly make a great effort to ensure that we carefully nurture your embryos so that they can develop into advanced stage embryos. We culture embryos to the blastocyst stage (usually around day 5) so that we can identify and eliminate poorer quality embryos and avoid failed embryo transfers and/or miscarriages.
Learn More about our EMBRYO GRADING at our San Diego Fertility Center.