ICSI - Intracytoplasmic Sperm Injection

ICSI can be performed with either fresh sperm or thawed frozen sperm. Our expert scientists choose the ideal sperm from the sample. The ideal sperm is not too fat or too thin, with a tail that’s not too long or too short and is referred to as having normal morphology (shape/structure). Being able to identify morphologically normal sperm is a skill that our scientists develop over many years, with constant fine tuning, to select the ideal sperm for every egg. The ideal sperm will have not only the normal morphology but also good motility (movement).

It’s a real skill to spot a morphologically normal ‘ideal’ sperm cells - they need to have a certain shape and size in many parts of the sperm cell. These sperm have an oval head and a long tail which they use to help them swim. Men with infertility issues often make fewer such sperm, which is why sperm selection for ICSI is so vitally important.

The next thing to consider is sperm motility or movement. Essentially, a sperm with good motility is able to move itself around and penetrate an egg. This movement depends on the length and size of the sperm’s tail. Tails that are curly or doubled up can’t swim as efficiently.

In order to select the best sperm for ICSI, the embryologist places a small amount of washed and prepared sperm into thick viscous media. This slows the sperm down, making it easier to observe and identify the ideal sperm based on their shape, motility and trajectory (direction).

Once our embryologists have selected the most morphologically normal and vigorous sperm, they immobilise them by striking their tails with a glass injection needle. True story!

They then aspirate (suck up) a single sperm into the needle tail-first, ready to be injected into the egg.

First, our embryologist places the egg in a customised dish under a microscope, moving it using advanced micro-manipulators. Next, they search for the ideal sperm for injection and immobilise this sperm and position it in the injection pipette. Then, they use a holding pipette to secure the mature egg in place. Finally, a thin, sharp glass micropipette - loaded with a single sperm - pushes first through the zona pellucida (the outer egg casing) and then the oolemma (the cell membrane of the egg) to enter the egg’s centre (the cytoplasm). The embryologist deposits the sperm ever so delicately into the centre of the egg.

In other words, our scientists do all of the work for the sperm - there’s no swimming or penetration of the egg involved. The only thing left for the sperm to do is to fertilise the egg.

After the ICSI procedure, we place the egg into our specialised culture incubators to assess for fertilisation ~17 hours later the next day, looking for signs or normal fertilisation, 2 pronuclear bodies known as ‘pronuclei’. These pronuclei are the genetic nucleus from the egg and sperm, so we need to see only two pronuclei, one from the egg and one from the sperm. If the egg does not present with 2 pronuclei, then the egg has not fertilised and will not produce an embryo.