In vitro fertilization (IVF) by ICSI is an advanced assisted reproductive technique used when there is a severe male factor infertility or when conventional IVF methods have been unsuccessful. Unlike traditional IVF, in which the egg is mixed with the sperm in the laboratory for fertilization to occur spontaneously, in ICSI a sperm is directly introduced into the egg through a highly controlled and precise process called intracytoplasmic microinjection.
In Vitro Fertilization through ICSI (Intracytoplasmic Sperm Injection)
What does the IVF technique by ICSI consist of?
The ICSI process shares several phases with traditional IVF until the moment when the eggs are obtained and prepared in the laboratory. From that point on, the treatment differs significantly. Below, we describe the key phases of ICSI:
1. Controlled ovarian stimulation and oocyte retrieval
The patient undergoes hormonal treatment to stimulate the growth of multiple follicles in the ovaries. Once the follicles reach the appropriate size, follicular puncture is performed, a minimally invasive procedure by which eggs are retrieved. These oocytes are collected for processing in the laboratory.
2. Denudation of the oocytes
The retrieved eggs are surrounded by a layer of cells that must be removed to assess the maturity of the oocytes. This process of removing the surrounding cells is known as “denudation”. Only oocytes that have reached the Metaphase II stage, which is approximately 80%, are suitable for sperm microinjection.
Sperm Microinjection (ICSI)
The ICSI procedure is performed using a specialized micromanipulator, which includes an inverted microscope that allows observation of the oocytes and sperm at 400x magnification. Using a micromanipulation arm, the oocyte is gently held, while the selected sperm is introduced directly into the cytoplasm of the egg with another microinjector arm. This ensures fertilization, even in cases of low sperm motility or quality, and guarantees that a single sperm penetrates the egg, reducing the risk of fertilization failure.
4. Embryo culture in controlled incubators
Once the sperm are injected, the oocytes are placed in incubators that replicate the physiological conditions of the human body. The temperature is kept constant at 37°C and the CO2 concentration is adjusted to 6%. This controlled environment ensures the best conditions for fertilization to occur. Approximately 1618 hours after microinjection, successful fertilization is assessed.
5. Embryonic development and transfer to the uterus
The fertilized eggs, now converted into embryos, are left to develop in the laboratory until day 5 or 6, when they reach the expanded blastocyst stage. This process, known as prolonged culture, allows a more precise embryo selection, increasing implantation and pregnancy success rates.
6. Cryopreservation of surplus embryos
If more good quality embryos are obtained than are needed for the initial transfer, they can be cryopreserved for future use. This avoids the need for a new ovarian stimulation in case the patient desires a second attempt at pregnancy or a future embryo transfer.
Advantages of IVF by ICSI
- High success rates in cases of severe male infertility: ICSI is the preferred option when sperm count is extremely low, sperm have motility or morphology problems, or there are difficulties in obtaining viable sperm.
- Precise control of the fertilization process: By injecting the sperm directly into the oocyte, the need for the sperm to pass through the natural layers of the egg is eliminated, thus overcoming physiological barriers that may be causing infertility.
- Optimization of the use of available oocytes: ICSI maximizes the chances of fertilization in cases where few oocytes have been retrieved, making the best use of each one of them.
Application of ICSI in different cases
ICSI is recommended in a wide variety of situations, including:
- Men with severe semen quality problems (oligozoospermia, asthenozoospermia, teratozoospermia).
- Previous cases of fertilization failure in conventional IVF cycles.
- Infertility caused by blocked or damaged fallopian tubes.
- Presence of antisperm antibodies in man or woman.
- Men who have resorted to sperm retrieval procedures (testicular biopsy or epididymal aspiration).
In short, IVF with ICSI is a cutting-edge technique that offers an effective solution to couples facing complex fertility problems, providing the possibility of achieving pregnancy even in the most difficult circumstances.
