What is intra-cytoplasmic sperm injection (ICSI) and how does it work?

Intra-cytoplasmic sperm injection (ICSI) involves injecting a single sperm directly into an egg in order to fertilize it. The fertilized egg (embryo) is then transferred to the woman’s womb.

The major development of ICSI means that as long as some sperm can be obtained (even in very low numbers), fertilization is possible.

Is ICSI for me?

ICSI is often recommended if:

  • the male partner has a very low sperm count
  • other problems with the sperm have been identified, such as poor morphology (abnormally shaped) and/or poor motility (poor swimmers)
  • at previous attempts at in vitro fertilization (IVF) there was either failure of fertilization or an unexpectedly low fertilisation rate
  •  the male partner has had a vasectomy and sperm have been collected from the testicles or epididymis (sperm reservoir)
  • other situations where the sperm count is zero and donor insemination is not wanted
  • the male partner does not ejaculate any sperm but sperm have been collected from the testicles
  •  the male partner has had problems obtaining an erection and ejaculating. This includes men with spinal cord injuries, diabetes and other disorders.

How does ICSI work?

The procedure for ICSI is similar to that for IVF, but instead of fertilisation taking place in a dish, the embryologist selects sperm from the sample and a single sperm is injected directly into each egg.

For women

Step 1. You take fertility drugs to stimulate your ovaries to produce more eggs, as for IVF.

Step 2. The eggs are then collected and each egg is injected with a single sperm from your partner or a donor. After two to three days in the laboratory, those that are fertilised are transferred to your womb in the same way as for conventional IVF.

Any suitable remaining embryos can be frozen for future use.

Step 3. Some clinics may also offer blastocyst transfer, where the fertilised eggs are left to mature for five to six days and then transferred.

Step 4. After the treatment, your clinic will arrange a date with you for your pregnancy test.

For men

Step 1. An embryologist will examine your sperm under a microscope and decide whether ICSI could increase your chances of fathering a baby.

Step 2. The next step depends on whether you are able to provide sperm without medical intervention:

If you can, you produce a fresh sperm sample on the same day as your partner’s eggs are collected.


Sperm can be collected directly from the epididymis (a narrow tube inside the scrotum, where sperm are stored and matured) using a type of fine syringe. This is known as ‘percutaneous epididymal sperm aspiration’ or PESA.

Sperm can also be retrieved from the testicles, a process known as ‘testicular sperm aspiration’ or TESA.

It is also possible to remove tiny quantities of testicular tissue from which sperm can be extracted. This procedure is called ‘testicular sperm extraction’ or TESE.

For more information about PESA, TESA and TESE, speak to your doctor.

Step 3. A single sperm is injected into each egg. This does not mean that the egg is fertilised, but ICSI now gives an opportunity for that complex process to commence. ICSI is not a guarantee that fertilisation will take place.

Step 4. Subsequently one – three of the best quality embryos are transferred to the womb.

In case of zero sperm count

If you have a zero sperm count (other than caused by vasectomy), the chances of retrieving sperm surgically by PESA, TESA or TESE may be very low or at least uncertain.

In this situation, consider having a surgical retrieval such as a ‘dummy run’ and store any sperm that are obtained. If no sperm are retrieved the options of having Donor insemination (DI) or In vitro fertilisation (IVF) with donor sperm can be considered instead.



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