ICSI is the microinjection of a spermatozoon into the cytoplasm of an oocyte. Although the technique emerged in response to cases of what was considered to be male sterility, today it is the most common procedure used for the fertilisation of oocytes in the laboratory.
It is advised in all cases where any alteration in sperm parameters has been observed via the seminogram, and there is little chance of fertilisation. For example where the number of spermatozoa with good motility or with normal morphology is low (oligozoospermia, asthenozoospermia, teratozoospermia, cryptozoospermia, necrozoospermia and combinations of these pathologies), and cases where sperm cannot be easily retrieved from the ejaculate (retrograde ejaculation). Also where there is no sperm in the ejaculate, and testicular sperm extraction needs to be carried out (obstructive azoospermia, vasectomy…), cases where we are working with a sample that has previously been frozen prior to chemotherapy or radiotherapy treatment etc.; in samples obtained from individuals suffering from an infectious disease which therefore need to be processed in a specific way in order to avoid transmission to the offspring.
In addition to its use in cases where there are problems with the sperm, the procedure has become much more widely used. It is employed in case of many couples where the cause of sterility has not been identified as lying with the male, to increase fertilisation rates in general, and in all cycles where genetic screening of embryos is needed.