ICSI is a method used for fertilization of an egg during IVF. Intracytoplasmic Sperm Injection was first developed as a fertility treatment for couples in which the male had low sperm counts or low sperm motility. Without ICSI, these couples had a high rate of fertilization failure using standard IVF. Since its introduction, ICSI revolutionized the treatment of male fertility. ICSI has been so successful, that it is used as the fertilization method of choice for most couples.
All methods of fertilization, including ICSI, take place in a special laboratory where all conditions are sterile. The temperature and air quality in the laboratory are carefully controlled.
The eggs are removed from the ovary after the patient administers the hCG trigger injection. The hCG plays an important role; it stimulates the egg to divide into two unequal cells. The larger cell is the mature egg that will be fertilized using ICSI. The smaller cell is called a polar body. During the egg retrieval, an attempt is made to obtain eggs from follicles of all sizes. As a result, some of the eggs will be immature and therefore are incapable of being fertilized. Other eggs may be degenerated or appear abnormal under the microscope. In order for an egg to be fertilized, it must be mature and healthy. Immediately after the egg retrieval, it is difficult to determine whether an egg is a mature egg. This is due to the fact that each egg is covered with thousands of small cells called granulosae cells. Special enzymes are used to clear the granulosae cells away and allow clear visualization of the egg before ICSI IVF is attempted.
The semen sample is then processed in order to obtain an optimum sample for Intracytoplasmic Sperm Injection. Under the microscope, a single sperm is picked up into a tiny glass pipette. The sperm is injected into the egg by passing the pipette through the surface of the egg. This works very well with a couple facing low sperm motility. The sperm cell is released and the pipette is withdrawn. At this time, a second polar body is released from the egg.
Eggs are fertilized using the ICSI procedure in order to maximize the rate of fertilization and to reduce the chance for fertilization failure. In the days before ICSI fertility, eggs were fertilized in a different manner. The egg was placed into a laboratory dish surrounded by growth fluids. Thousands of sperm were deposited into the fluid surrounding the egg. The sperm were required to swim to the egg, penetrate the granulosae cells, and fuse with the surface membrane of the egg in order to achieve fertilization. Studies demonstrated that about 5% of the time, fertilization would fail even if the man had a normal semen test.
Occasionally, even with ICSI, fertilization does not occur, or occurs abnormally. This usually happens when there are very few eggs available to inject with sperm or when the eggs are of poor quality. Ordinarily, using ICSI, about 70% of the mature, healthy eggs should fertilize normally.
After the sperm are injected into the egg, the egg is placed back into the incubator. The next morning, the injected eggs are inspected under the microscope to determine whether fertilization occurred normally. I will call my patients the day after the retrieval to let them know how many of the eggs fertilized normally.