Conventional IVF involves placing the egg from the female partner together with many thousands of sperm prepared from a semen sample provided by the male partner, and allowing the process of fertilisation to take place over a number of hours in the culture dish.  However, for many couples this technique will be unlikely to result in fertilisation either because the number of sperm available is insufficient or because there is reason to believe that the sperm will be unable to penetrate the egg. In such cases the technique of IntraCytoplasmic Sperm Injection (ICSI) is usually applied.

Together with IVF, ICSI is one of the most common techniques used in Assisted Reproductive Technology, and many thousands of babies have been born worldwide since it was introduced.  It involves the direct injection of a single sperm into each egg using very fine micromanipulation equipment. Given that the human egg is one tenth of a millimetre in diameter, this is a very delicate procedure performed by highly skilled embryologists.  The technique can also be used in conjunction with sperm which has been obtained surgically from the male reproductive tract when sperm are not present in the semen.

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