IMSI stands for intracytoplasmic morphologically-selected sperm injection. It's an assisted reproduction technology inspired by ICSI (intracytoplasmic sperm injection), which was developed in the 1990s. IMSI first became available in 2004. Both ICSI and IMSI are used to increase the chances of fertilization during the IVF procedure. How? By injecting a sperm cell directly into each of the selected eggs retrieved from the female partner's ovaries.
Only The Best Will Do
IMSI is particularly effective in combating male factor infertility. This is because the IMSI specialist uses a high-powered microscope to select the healthiest sperm cells for injection into the eggs.
Men who have low sperm counts or poor quality sperm cells benefit from this more than they do from say, conventional IVF. This is because sperm cells and egg cells are simply mixed together during IVF, in the hope that the sperm will be strong enough to fertilize the eggs. Sometimes this is not the case.
ICSI and IMSI are very similar procedures - basically the only difference between them is the strength of the microscope used to select sperm cells in IMSI. The IMSI microscope is five times more powerful than conventional microscopes used in other forms of assisted reproduction treatment. This gives the fertility specialist a huge advantage when it comes to picking out the sperm cells with the best structure and motility.
What Makes A Good Sperm Cell?
The healthiest sperm cells have a certain shape and size. Men suffering from infertility often don't have many of these sperm cells in their semen, making it all the more important that the microscope tracks them down where they do exist.
Shape - the best sperm cells have an oval head and a long tail which they use to push themselves along as they swim. These are the ones that the IMSI specialist will pick out and inject directly into an egg. Sperm cells with abnormally shaped heads will not be used, if at all possible.
Motility - a sperm cell's motility is its ability to move itself around and penetrate an egg. This depends on the length and size of its tail. Tails that are curly or doubled up aren't as efficient when it comes to swimming.
After the female partner has taken ovulation-inducing drugs, and had her mature eggs retrieved in the fertility clinic (just as she would during IVF), the IMSI specialist selects the sperm cells he wants to use and then prepares to inject one into each egg. Under a microscope, he uses a specialized pipette to secure the egg in place, and a long, thin, hollow needle to pick up the sperm cell he wants and inject it into the egg. He pushes the sperm cell all the way into the egg's inner cytoplasm. In other words, he does the sperm cell's work for it - no swimming or penetration involved! The egg and sperm cells are then left for 24 hours, at the end of which there's a very good chance that fertilization will have occurred. The fertilized eggs (embryos) are then inserted into the woman's uterus.
Studies have found that IMSI more than doubles the chances of a successful pregnancy resulting from IVF treatment. Skeptics argue, however, that there really isn't much difference between IMSI and ICSI - ICSI specialists also seek to select the best sperm cells, after all. Some medical experts are concerned about the possible impacts of IMSI on the long-term health of the resulting baby. They think that genetic problems in weak sperm cells could be passed on to the next generation.
Basically, the jury is still out. IMSI is too recent a development for us to have access to any long-term data. One thing on which the experts do agree is that further monitoring and study is required.