The mysterious world of the embryology laboratory

In vitro fertilization (IVF) is now considered one of the greatest successes of modern medicine. This is the most effective treatment at the fertility clinic.

It consists of several stages, including ovarian stimulation, egg collection, laboratory fertilization and embryo transfer into the uterine cavity.

After egg collection is done by a doctor, the whole process of fertilizing and monitoring the embryo is carried out in a confined world of embryology laboratories before embryo transfer.

Preparation
During the puncture, the embryologist proceeds to identify the cumulo-oocyte complex (CCO), it is an ovule surrounded by a layer of cells (cumulus). A dozen CCOs recover on average, but this number varies from one cycle to another, depending on the response to ovarian stimulation. The CCO was then placed in an incubator at 37 ° C for 2 hours.

Along with egg preparation, spermatozoa are prepared. They are centrifuged on the density gradient and washed to choose the most mobile and most morphologically beautiful.

That meeting
There are two ways to achieve conception: conventional IVF and IVF are assisted by intracytoplasmic sperm injection (ICSI). For conventional IVF, CCO is cultured with sperm in a petri dish placed in an incubator at 37 ° C overnight. It’s up to the sperm to make their way to meet the egg.

For ICSI, the embryologist arranged this meeting. For this, it is necessary to prepare eggs: it is a decoration. This is done thanks to mechanical and enzymatic actions. Thus the cumulus cells will be separated from the egg. Before microinjection, it is necessary to check the maturity of the egg due to the presence of polar blobs. Indeed, immature eggs cannot be fertilized.

Spermatozoa are then observed under a microscope (sometimes at high magnification: IMSI), to select the best candidate. This can sometimes also be done by PICSI. In a more conventional way, the choice of sperm to be injected is based on several criteria. Mobility and movement are the first selection criteria because it is a guarantee of living spermatozone. Then, the size of the flagella, neck and head of the spermatozoa is carefully evaluated. After selection, the embryologist paralyzes the spermatozoon by mechanical action on the flagellum and sucks it through a micro injection pipette. The cooked egg is then held by a compression pipette and spermatozoon is injected into it. This technical movement must be controlled perfectly so as not to smear the eggs. The eggs are then placed in an incubator at 37 ° C for the night.

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