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imsiThis technique is similar to the above up to the laboratory phase, where fertilisation is carried out by “intracytoplasmatic sperm injection” (ICSI).

The injection is made on the oocytes that show correct maturing (approximately 80%), that is, those in Metaphase II. To do so, we must free them from the cells that surround them. This process is known as “decumulation”.

The sperm injection is carried out with a micromanipulator. The microinjector comprises an inverted microscope (which allows us to observe the oocytes and the sperm with up to 400x zoom) and some microinjector arms. One of them is used to hold the oocyte to the injector by means of suction, and the other hydraulic arm is used to capture the sperm and introduce it into the oocyte, enabling fertilisation.

Subsequently, the injected oocytes are kept in conditions as close as possible to physiological conditions. This is achieved by keeping the oocytes in an incubator, with a stable temperature of 37º C and 6% of CO2, until their fertilisation is checked 16-18 hours after the microinjection.

Two or three days (day +2 or +3) after fertilisation, the pre-embryos are transferred to the inside of the uterus, and should there be any supernumerary pre-embryos, they will be cryopreserved to make another transfer, thus avoiding the need for another ovarian stimulation.

In both techniques, should we obtain supernumerary pre-embryos, these can be kept in “prolonged cultivation” until the expanded blastocyst phase, performing the transfer on day +5 or +6, making it possible to better select the embryos and therefore leading to a greater number of pregnancies.

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Written by: Sabrina Camara