ICSI Through the Eyes of an Embryologist
The intracytoplasmic sperm injection (ICSI) procedure is one of the most precise methods of fertilization used in reproductive medicine. On the day of oocyte retrieval, the embryologist carefully locates the oocytes under a microscope and places them in an incubator for several hours. The oocytes are then cleaned of the cumulus-oocyte complex, and mature cells are selected based on the presence of the polar body in the perivitelline space.
The next step is preparing the semen for fertilization. Two techniques are commonly used for this: the Swim-up method or gradient centrifugation, both aimed at isolating the most motile and morphologically normal sperm cells. The fertilization process takes place under a microscope at high magnification, allowing the embryologist to select the most viable and properly formed sperm cell. The main criteria for selection include:
Motility: The sperm must move in a straight line at a speed of 25 microns per second or more.
Morphology: The sperm should have a normal and proportional structure.
Once the sperm is selected, the ICSI procedure begins. This is performed in microdroplets of a special culture medium, where the oocytes are ready for fertilization.
Stages of ICSI
The ICSI procedure consists of four main stages:
Immobilization of the sperm — The sperm is immobilized by carefully damaging its tail with a needle.
Aspiration of the sperm — The sperm is aspirated into a very fine needle, which is used to pierce the zona pellucida of the oocyte.
Fixation of the oocyte — The oocyte is secured using a suction tool.
Injection — The sperm is injected into the cytoplasm of the oocyte through the puncture in the zona pellucida.
Indications for ICSI
ICSI is indicated in the following cases:
Male factor infertility characterized by low sperm parameters.
Use of sperm retrieved through surgical methods.
Fertilization of oocytes after cryopreservation.
Immunological infertility (positive MAR test over 50%).
Cases involving preimplantation genetic testing (PGT) planning.
To increase the effectiveness of ICSI, it may be combined with the PICSI method, which physiologically selects sperm for injection.
How ICSI is Performed
ICSI is similar to traditional IVF, but with the key difference that the sperm is injected directly into the oocyte. This technique is particularly important for couples with significant male factor infertility or when previous attempts at fertilization have been unsuccessful. ICSI is also commonly used in cases associated with surrogacy programs, where high-quality embryos need to be produced for future implantation.
The procedure consists of several steps:
Ovarian stimulation: The patient is prescribed hormonal medications to stimulate the maturation of multiple oocytes.
Oocyte retrieval and sperm collection: After stimulation, a vaginal puncture is performed to retrieve the mature oocytes, while the partner provides a fresh sperm sample.
ICSI (Sperm injection into the oocyte): Each oocyte is fertilized by injecting one sperm directly into it.
Embryo transfer: A few days after oocyte retrieval, the embryo is transferred to the uterus.
The Role of the Embryologist in ICSI
The success of ICSI relies heavily on the precision and expertise of the embryologist. Every stage, from the selection of the oocytes to the injection of the sperm, is performed under the control of advanced technology. This method significantly improves the chances of successful fertilization and embryo development, especially in complex cases of male infertility.