The process of oocyte fertilization is a central step in the in vitro fertilization (IVF) procedure, where mature oocytes, collected from the ovary, are joined with sperm to form embryos that will later be transferred to the uterus.
This stage takes place in the laboratory and requires controlled conditions to maximize the chances of fertilization and healthy embryonic development.
The collected mature oocytes are identified and selected for fertilization. They are removed from the collection medium and placed in a special environment, ready to support the fertilization process.
Sperm can be prepared before fertilization. If necessary, sperm are separated from other sperm components, and the most motile and healthy sperm are selected for use in the fertilization process.
There are two main techniques used for fertilization in IVF:
a. Conventional fertilization (classic IVF): Mature oocytes are placed in a culture medium and are directly exposed to selected sperm, allowing fertilization to happen naturally. Sperm are brought into contact with oocytes and one of them is expected to enter the oocyte membrane and fertilization takes place.
b. Intracytoplasmic sperm injection (ICSI): This technique involves injecting a sperm directly into the oocyte using a micro-needle.
This is a more precise process and is used in case of severe sperm problems or in situations where conventional fertilization can be more difficult.
After fertilization, the oocytes are monitored to check whether fertilization has occurred. The formation of pronuclei, which are the nuclei of egg and sperm cells, is checked, thus signifying that fertilization has been successful.