Understanding the fertilization stage
As soon as the eggs have been retrieved, they will be washed in a solution to get rid of the sticky cumulus cells that surround them. These cumulus cells are from the follicular fluid, and they make it difficult for the embryologist to determine the quality or even the presence of an egg. The mature eggs are moved to an incubator for several hours to prepare them for fertilization. While all of this is happening, your partner’s sperm is also undergoing certain preparations. The obtained sperm sample will be washed in a solution and divided into 100,000 sperm per millimeter.
As soon as both sperm and egg are ready, the two will be combined in a manmade culture medium designed to simulate the environment of the fallopian tube. The culture medium will also protect the embryos as they slowly develop. The petri dish containing the sperm and egg will be returned to the incubator and left alone for several days so the embryo can develop undisturbed.
Intracytoplasmic sperm injection (ICSI)
Some fertility clinics recommend a procedure called intracytoplasmic sperm injection (ICSI) to increase fertilization success among couples suffering from male factor infertility. ICSI makes use of a microscope and a hollow, microsized needle to obtain a single, healthy sperm cell from a sample. The sperm is injected into the cytoplasm or center of the egg using the hollow needle. Some couples worry that ICSI babies might be at risk for genetic diseases, delayed development, or health problems because it makes use of sperm that was incapable of fertilizing naturally. However, the vast majority of ICSI babies are born healthy and experience normal childhood development. Research also show that the percentage of ICSI babies with genetic problems do not exceed that of babies conceived normally.
No matter how excellent your eggs are, only 70% of them will become embryos. This is due to the stringent monitoring system of fertility clinics; your embryologist will only transfer the healthiest ones into your uterus. The first examination happens several hours after insemination, to confirm that each egg got fertilized. Those that did not fertilize will be discarded. The remaining embryos will be left alone for over 24 hours and inspected once again to check their cell division. At this point, the embryos should have divided into two or four cells. You may choose to have your embryos transferred at this time, but most doctors recommend transfer during the blastocyst stage, when the embryos have divided into at least 12 cells.