What is IMSI (Intra-Cytoplasmic Morphologically Selected Sperm Injection)?

Science is constantly trying to advance techniques used in IVF to improve the chances of fertilisation and a healthy pregnancy. These are the two objects of the procedure, which is designed to give infertile and same sex couples, as well as single mums, a chance to get pregnant and have their own child. ICSI, a convenient abbreviation for intra-cytoplasmic sperm injection, has been used since its inception to increase the chances of a successful IVF to great effect, but now a new refinement on this procedure called IMSI can potentially increase the chances of a successful IVF pregnancy, two-fold.

What is IMSI and how is it different from ICSI?

To properly explain IMSI we should take a quick look at ICSI. As amazing as IVF is, the chances of success have always been a bit of a cause for concern, not so much in recent years as some clinics can boast extremely high success rates, but it remains something that doctors and scientists are constantly trying to improve. The dream is that one day all it will take is one cycle of IVF, which can save you the emotional and financial stress of having to go through multiple cycles of IVF as is often needed now. ICSI was a big step forward towards realising this dream, and hugely improved the success rate of IVF where used, but why?


Essentially ICSI is the direct injection of a sperm cell into an egg cell, a process which removes chance from the equation as there is no element of the sperm cell having to access the egg, penetrate it, and then fertilise it. Male infertility often stems from one of these stages, problems with poor sperm motility, count, and structure all lower the chances of a successful fertilisation and pregnancy. What ICSI does is directly introduce the sperm cell to its female equivalent, the egg cell, hence removing these other factors which affect success.

This was an amazing advancement at the time and the proof was in the pudding as IVFs where ICSI was performed were far more successful, however, as always, there remained room for improvement. This improvement was in the form of IMSI, which adds another dimension to ICSI by introducing a step in which the best possible sperm cell is selected to almost double the chances of fertilisation.

How does IMSI achieve this remarkable feat? Simply through the use of an extremely powerful microscope to pick out the best sperm in a sample, and then by making use of that sperm in the ICSI procedure. By ‘best sperm’ we mean one that is best suited to its task, and the signs of quality that a specialist will look for are things like shape, motility, etc.

What exactly is involved in IMSI?

A high powered microscope is used to pick out and the best sperm cells which are then used in a traditional ICSI protocol.

In a normal ICSI procedure sperm is put into a dish with polyvinylpyrrolidone (PVP), this slows the sperm down in order for it to be analysed to assess which sperm are of the best quality. The tails of the sperm are squished with a fine, hollow needle and are then sucked up the needle. The egg is held in place and prepared using an enzyme called hyaluronidase which gets rid of its surrounding cumulus cells. The cumulus cells are present so that in natural fertilisation, once a sperm has entered the egg, the shell of the egg can harden to prevent other sperms from entering. A single sperm is injected directly into the eggs cytoplasm. Using a fine hollow needle the membrane of the egg is pierced and the sperm is then passes through the needle.

Why should I have IMSI? Is it suitable for me?

IMSI is a good choice for anyone who has failed IVF cycles in the past, and for couples who have a component of male infertility. Unfortunately further reports need to be made to show the benefits of using IMSI and evaluate the costs. It is estimated that IMSI is twice as expensive and will require further specialist training and equipment, meaning that not everyone will be able to afford the procedure on top of the existing cost of IVF. What IMSI does promise, however, is another step towards quicker, more efficient, and reliable assisted reproduction.

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