Intracytoplasmic Sperm Injection (ICSI)

ICSI is part of the whole IVF (In Vitro Fertilization) process. During a normal menstrual cycle, only 1 egg is usually recruited to mature in a capsule of fluid called a follicle. The maturation time of the egg inside the follicle, is usually 10-14 days. Most follicles measure about 16 – 20 mm when the egg is mature. At this time during natural ovulation, the follicle ruptures and the egg is released.

During IVF, fertility drugs are used to stimulate the ovaries and recruit a bunch of eggs. So instead of just one follicle maturing, a whole number of follicles are stimulated to grow. These follicles are monitored by ultrasound, and when they reach maturity the eggs are surgically retrieved. For retrieval, a fine needle is passed through the vagina and into the ovaries, where eggs are aspirated from the follicles.

Concurrently the sperm is prepared. Sperm may be collected from an ejaculated specimen of semen, or prepared from a previously frozen surgically retrieved specimen. The eggs are then stripped of the cumulus cells (which are the sunburst array of cells around the egg) The cells are removed to assess the maturity of the egg, to better visualize the egg during the ICSI process, and to prevent the inadvertent injection of DNA from the cumulus cells into the egg. The stripping is done with an enzyme called hyaluronidase, which is normally found in the sperm heads. In normal fertilization it is this enzyme that allows the sperm to digest their way through the cumulus cells to the egg.

A tiny collection of sperm is placed in a viscous solution called “sperm crash” – and this slows down the motility of the sperm making them more easily assessed and caught. A healthy sperm is identified and then immobilized by striking the tail with a tiny glass needle called the injection pipette. The sperm is then aspirated tail-first into the same glass pipette. Using a high-powered microscope with sophisticated manipulation equipment, the egg is located and held in position by a holding pipette. The injection pipette is inserted into the egg thereby tenting the membrane – and gentle suction applied until the elastic membrane is broken. Once the membrane is broken the sperm can be deposited into the egg and then the injection pipette is removed. Once the pipette is removed the egg will resume its normal shape and is then put into a specialized culture medium in an incubator. It is then assessed for fertilization 18 to 20 hours after the injection.