Fertilization of Eggs

Once the eggs are retrieved and placed in the incubator, they rest for several hours before the sperm is added, usually in the afternoon of the egg retrieval. Addition of sperm to the culture media is called insemination, and is followed by fertilization, when the sperm enters the egg. Fertilization can also be accomplished by ICSI (intracytoplasmatic sperm injection). ICSI will be recommended if your physician suspects that there will be a significant chance of no fertilization or a low rate of fertilization with conventional insemination of the oocytes in the laboratory.

We will call you the day after retrieval to let you know how many eggs have fertilized. It is important to understand that all the embryos may not be able to be observed on that day and that of those that are seen, they may not continue to grow. The embryo can begin cleaving, or dividing, first into two cells, then into four. Cleavage to four cells generally takes 36-48 hours or more after the egg retrieval. After 3 days, an embryo which is growing properly will have 6-8 cells. An embryo should reach a blastocyst stage at 5-6 days after retrieval.

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