This technique is similar to the previous one until the laboratory phase, where fertilisation is carried out by means of “Intracytoplasmic Sperm Injection” (ICSI).
In Vitro Fertilisation by ICSI
The IVF technique using ICSI
The microinjection will be carried out in oocytes that have matured correctly (approximately 80%), i.e. those that are in Metaphase II. To do this we must free them from the cells that surround them. This process is known as “denudation”.
We use a micromanipulator to perform the sperm microinjection. The microinjector consists of an inverted microscope (with which we can observe the oocytes and spermatozoa at up to 400x magnification) and microinjector arms. One of them is used to hold the oocyte to the microinjector by means of suction, and the other hydraulic arm is used to capture the spermatozoa and introduce it into the oocyte, thus facilitating fertilisation.
The method
Subsequently, the microinjected 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% CO2, until fertilisation is verified 16-18 hours after ICSI.
Two or three days (day +2 or +3) after fertilisation (ICSI), the pre-embryos are transferred into the uterus, and if there are supernumerary pre-embryos, these can be cryopreserved for another transfer, thus avoiding having to undergo stimulation again.
In both techniques, in the case of obtaining supernumerary pre-embryos, these can be kept in “prolonged culture” until the expanded blastocyst stage, carrying out the transfer at day +5 or +6, allowing for better embryo selection, and therefore a greater number of pregnancies.
