Intracytoplasmic Sperm Injection (ICSI) is a specialized form of In Vitro Fertilization (IVF) that is used for the treatment of severe cases of male factor infertility. ICSI involves the injection of a single sperm directly into a mature egg.
Before ICSI can be done, mature eggs must be retrieved from the female partner during a standard IVF cycle. The male partner’s semen sample is prepared in the lab to isolate as many healthy moving sperm as possible.
After allowing the eggs to rest for two to three hours following their removal, the tight outer coating of cells (cumulus) is removed from each egg. Only then can we be sure the egg is mature enough to undergo ICSI.
Immature eggs cannot be injected. However, they can be incubated for a further two to six hours and reassessed. If they mature in that time they can still be injected along with the other mature eggs. A special instrument is used to hold the egg in place. It is so small you can barely see the tip with the naked eye.
A thinner, sharp, needle-like instrument is used to pick up a single normal appearing sperm. With great precision, the needle is inserted through the egg’s outer coating (the zona pellucida) and into the egg itself. The sperm is slowly injected into the egg, and the needle is removed, leaving the sperm behind.
The injected eggs are placed in an incubator overnight and checked the next morning for signs of fertilisation.
After an additional 24 hours, we can determine how many have divided and gone on to form embryos. Not all eggs fertilise, and not all fertilised eggs become embryos. As with standard IVF, the number of embryos replaced into the uterus depends on the woman’s age and medical history.
Provided they appear healthy, additional embryos can be frozen if desired. The potential improvement in fertility that this type of treatment may yield depends on the woman’s age, diagnosis and the initial male semen analysis, and should be discussed with your specialist
Couples who have had poor or no fertilisation during standard IVF, as well as men who have:
For the egg:
As ICSI is more invasive and requires more handling than standard IVF insemination techniques, there is a small chance (<2%) that the egg may be damaged during the procedure – resulting in a non-viable egg.
For the resulting child:
Thousands of children have been born around the world as a result of ICSI. To date, there is no convincing evidence that the incidence of birth defects is any different with ICSI or IVF as compared to those children born to other parents of similar age and health.
The mother’s age at delivery, family history and the presence of pregnancy complications are the most important predictors of newborn health. However, it is possible that a male child born as a result of ICSI might have a fertility problem, similar to his father or slightly different.
Some men have an acquired cause of their sperm problem that we know will not be hereditary (i.e. vasectomy, spinal cord injury, etc.). However, other men have sperm problems that may have been present since birth. These may be passed on to the male children due to a small chromosomal rearrangement, a deletion of a small portion of the Y chromosome, etc. As well, men with very low sperm counts or an obstruction in their sperm ducts (vas or epididymis) may carry one of the cystic fibrosis genes (CF). In this situation, the child may inherit the cystic fibrosis gene, and if the female partner also carries one of the cystic fibrosis genes, there is a chance of producing a child who actually has cystic fibrosis.
Just as the mother’s age influences the risk of birth defects, men with very low sperm counts also have an increased risk (about 1%) of producing a son with an abnormal number of sex chromosomes (i.e. XXY or XYY instead of the usual XY). These children have a normal physical appearance and are likely to have normal IQ scores, but they may develop learning difficulties, behaviour problems or infertility.
Blood tests can be done to screen one or both partners for many (but not all) of these problems, including chromosomal rearrangements, cystic fibrosis carrier status, etc. Genetic testing is also available during the pregnancy (i.e. amniocentesis or CVS) to look for many of these abnormalities.