IntraCytoplasmic Sperm Injection (ICSI)

ICSI is a technique allowing microinjection of a single sperm into the egg. The embryologist selects a single live sperm, immobilizes it before injects it directly into a healthy mature egg using a fine pipette. The injected eggs are examined 16 – 18 hours later for evidence of fertilization. The normally fertilized eggs are cultured and monitored until the day of transfer. The day of embryo transferred can be 2, 3, 4 or 5 days after the injection and only the best embryos (usually 3 embryos) will be transferred.

ICSI can also be used in conjunction with IVF when the patient has history of failed fertilization in previous conventional IVF cycle, or when the quality of the sperm is considered to be too poor for a successful fertilization with conventional IVF.

ICSI and conventional IVF both share the same protocol for ovarian stimulation, follicular monitoring and egg collection. The sperm is prepared on the same day of egg collection regardless it is a fresh or frozen semen sample, and in same cases it involves surgically extracted sperm, such as MESA, PESA, TESA or testicular biopsy.

As ICSI bypasses the zona pellucida (egg shell) and deposits the sperm directly into the egg, ICSI results in higher fertilization rate and more embryos available for transfer than conventional IVF. In general, the success rate for ICSI is as good as or even better than conventional IVF.

This is the oldest form of Assisted Reproductive Technique, that involves the insemination of Cumulus-Oocyte-Complex with spermatozoa in a petri dish.

Prior to stimulation, the seminal fluid is processed and only the progressive sperm and adequate amount of sperm are inseminated.

The events that take place during IVF include:

Sperm penetration to the COC

Sperm penetration to the COC

Sperm-Egg Plasma membrane binding

As the sperm binds to the oolema, a protein in the egg activates and this blocks further sperm penetration to avoid polyspermy.

Sperm attaches and penetrates the zona (outer shell of the egg)

The sperm releases an enzyme that can penetrate the COC and the best sperm will penetrate the zona and finally to the plasma membrane.


After the sperm-egg fusion, the sperm’s head decondensed in the egg cytoplasm. A successful fertilization can be observed when a Male and Female pronuclei appears.