Intracytoplasmic Sperm Injection (ICSI)

Intracytoplasmic Sperm Injection (ICSI) is a Medically Assisted Reproduction technique that has made it possible to overcome causes of infertility that conventional In Vitro Fertilization (IVF) does not allow.

Unlike conventional IVF, in which several sperm are placed in contact with the oocytes, in ICSI only one sperm, previously selected, is injected directly into the cytoplasm of the oocyte. The steps of ICSI are similar in several respects to those of conventional IVF, but ICSI requires more preparation of the oocytes and the fertilization process requires specialized equipment, namely an inverted microscope with microinjectors, operated by  joysticks , to which small pipettes are attached.

ICSI can be performed using gametes from both partners (intraconjugal ICSI) in the case of a heterosexual couple. Alternatively, donated gametes, both oocytes and sperm, can be used.

ICSI is indicated in cases of moderate to severe male factor infertility, namely:

• Low sperm concentration in the ejaculate – Oligozoospermia
• Defects in sperm motility – Asthenozoospermia
• High percentage of morphological defects – Teratozoospermia
• Absence of sperm in the ejaculate – Azoospermia – in these cases, a testicular biopsy and ICSI with sperm recovered from the testicular tissue are indicated.

ICSI is also indicated in situations of fertilization failure in previous cycles of conventional IVF and/or Intrauterine Insemination, and in cases where Pre-Implantation Genetic Diagnosis (PGD) will be performed on the embryos obtained.

Although each case is treated individually and in a personalized way by our clinical team, we present here the general steps of an ICSI treatment. 

Ovarian stimulation

After a medical consultation and definition of the best protocol to follow, the woman’s ovaries begin to be stimulated from the 2nd day of her menstrual period. Stimulation is done using injectable hormonal medication that stimulates the growth of several follicles simultaneously, unlike the natural cycle in which, as a rule, only one reaches the necessary development for fertilization to occur. The medication used can be administered by the woman herself, at home.

After starting the medication, the growth of the follicles is monitored by ultrasound scans performed at intervals of approximately 3 days. When a reasonable number of follicles are in the pre-ovulatory stage (dimensions greater than 17 mm on ultrasound), another hormonal medication (hCG) is administered which will cause the final maturation of the follicles and the oocytes contained in them, as would happen in a natural cycle. 

Follicular puncture

36 hours after taking the hCG hormone, follicular puncture is performed. This is a quick surgical procedure, performed vaginally and under sedation, during which the fluid from the follicles is aspirated using a needle controlled by ultrasound.

From this day onwards, according to the defined protocol, you can start taking new medications (orally or vaginally) that will make the uterus more receptive to receiving the embryos and allowing their implantation. 

Gamete processing

The follicular fluid is sent to the laboratory and the presence of oocytes is observed. These oocytes are collected and treated so that ICSI is possible, that is, all the cells surrounding the oocyte are removed through a procedure called denudation. Denudation allows the maturity and quality of the oocytes to be assessed, and only mature oocytes will be able to be fertilized.

On the same day as the follicular puncture and at around the same time, an ejaculate sample must be collected by masturbation. The sample can be collected at the clinic or at home, provided that the sample is delivered to the clinic by the patient. The ejaculate sample is processed using appropriate means that promote the selection of sperm with normal morphology and motility. The processing of cryopreserved ejaculate or testicular tissue samples follows the same principles as the processing of “fresh” ejaculate samples.

ICSI

Once the oocytes and sperm have been processed, the microinjection procedure is prepared. To do this, an inverted microscope equipped with two microinjectors manipulated by  joysticks  (micromanipulators) is used, in which small pipettes are placed. One of the pipettes will hold the oocyte so that the other pipette can inject the selected sperm directly into the oocyte cytoplasm. 

Fertilization and embryo culture

16 to 18 hours after microinjection, fertilization is observed through the presence of two pronuclei (one female and one male) that will fuse in the following hours and give rise to embryos, through successive cell divisions. The embryos remain in culture in incubators with the appropriate atmosphere and in culture media that promote their development. An assessment of the development of the embryos is made daily. 

Embryo transfer and/or cryopreservation

3 to 5 days after microinjection, the best quality embryo(s) are transferred to the patient’s uterus. Embryo transfer is a quick procedure that does not require analgesia/sedation, in which one or more embryos are introduced into the uterine cavity using a catheter specifically designed for this purpose.

If it is not possible to transfer embryos in the cycle in which they were created (due to the risk of Ovarian Hyperstimulation Syndrome or another reason) or if there are more good quality embryos than can be transferred, these embryos are cryopreservated.

bHCG analysis

12 days after embryo transfer, a blood test is performed to detect the hormone bHCG, the pregnancy hormone.

The success rates of the ICSI technique, nationally and internationally, are around 30%.

The success rate is influenced by a variety of factors, the most important being the woman’s age, egg quality and sperm quality, so you should discuss your particular case with your doctor.