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ICSI (intracytoplasmic sperm injection)

  • Has revolutionised the treatment of infertility caused by male factors
  • A ‘microinjection’ IVF technique in which a single sperm cell is injected into the egg for fertilisation
  • Just one sperm is enough
IUI treatment LWC

ICSI: How it works

ICSI is an IVF technique in which a single sperm is injected into the centre of an egg. Today, it’s the world's favoured fertilisation method for all types of IVF, even though it was originally developed for the treatment of male infertility. The rate of fertilisation is generally around 90%, so many clinics use ICSI to guarantee fertilisation - even though success rates in non-male infertility are no different from those of IVF.

The early stages of ICSI treatment are the same as for conventional IVF. The female partner takes fertility drugs to stimulate her ovaries so that several eggs can be collected. Each egg is injected with a sperm cell so that several embryos will be available for transfer and freeze storage.

Each individual sperm cell is picked up in a very fine suction needle (many times smaller than a human hair) before injection. The whole process is visualised through very high magnification microscopes.

Side effects

Studies since the early 1990s show that the injection itself causes no damage to the egg or subsequent embryo. There has been long-term follow-up of ICSI babies, with no worrying problems reported. Thus, the most widely reported 'side effect' associated with ICSI is - as with IVF - a multiple pregnancy. There is also a very small risk that some women (1-2%) will over-react to the hormone drugs used to stimulate the ovaries (OHSS), but ultrasound and hormone monitoring during this drug treatment phase usually ensures that any over-reaction is foreseen and any risk avoided. Egg collection can be uncomfortable, and is often performed with a local anaesthetic.

Success rates

As with any type of fertility treatment, success rates will vary according to patient age and other circumstances. The LWC’s pregnancy and live birth rates from ICSI are recorded by the HFEA and can be found here.


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The London Women's Clinic