Day 0, Oocyte aspiration
During oocyte retrieval, the follicle fluid is aspirated from all follicles and examined in the laboratory for oocytes. At this time the oocyte is inside a cloud of cells called granulosa cells. Granulosa cells support oocyte maturation and development inside the follicle.
In-vitro fertilisation (IVF )
After a couple of hours the oocyte is mature and ready for fertilisation. The embryologist adds sperm to the oocyte at 12 o'clock, after which the spermatozoa themselves must find their way through the zona pellucida into the oocyte and fertilise it. The fertilisation process itself is normal. It does not just take place in the fallopian tube but in the incubator, which mimics the conditions inside the body. Two hours later, the embryologist controls that the cloud of granulosa cells has collapsed. It is a sign that fertilisation has occurred and surplus sperm are removed from the eggs.
When performing ICSI, the procedure is done shortly after 12 o'clock. The embryologist looks for a sperm with normal morphology and progressive forward motility and catches the sperm with a very thin glass tube called a pipette. She sucks the sperm into the pipette and then gently places the sperm inside the oocyte. In this way we optimize the possibility that fertilisation will take place.
However, fertilisation is a complex biochemical process by which oocyte and sperm must pair their chromosomes. Therefore, it is not certain that all oocytes will be fertilised properly, although the sperm entered the egg. Press the video link if you want to see how ICSI is performed.