3. Fertilization in the Laboratory
The obtained oocytes are taken to the IVF laboratory where they are prepared to be inseminated, depending on the technique being used IVF or ICSI. At the same time, the semen is prepared to improve and increase its fertilizing capacity.
To carry out in vitro fertilization in a conventional manner (IVF), the ovules or oocytes are kept with the surrounding cells (granulosa cells) that allow the sperm to interact with the ovule to fertilize. These ovules are placed in a plague and left in contact with the sperm.
In the case of a ICSI, we remove the cells that surround the ovule, as this allows the embryologist to see which a ovules are suitable to microinject (mature oocytes) so the cells are not necessary; in this case, a single sperm with the appropriate characteristics will be directly microinjected into the ovule.
The fertilized oocytes are confirmed the next day. From that moment, the embryos are kept in a culture suitable for their development. The embryos can remain in culture for 2 to 6 days anddepending on each case they will be transferred at the cell or blastocyst stage.
If the embryos have a thick membrane, embryologists may recommend assisted hatching, that is, decrease the thickness of the membrane and thus facilitate the embryo’s exit from its outer shell and adhere to the lining of the uterus so that implantation can occur.