Intracytoplasmic Sperm Injection (ICSI)

Shortened to ICSI/IMSI

Male factor infertility treatment that lets couples achieve similar success to those with other causes of low fertility

About ICSI and IMSI

ICSI treatment has allowed couples where there is a significant male factor problem to achieve treatment success similar to those with other causes of subfertility. Prior to its introduction in 1992, these couples would have not achieved fertilisation or very low fertilisation rates using standard IVF techniques.

Couples prepare for ICSI in the same way as for standard IVF, namely ovarian stimulation and egg collection. A single motile morphologically normal sperm is carefully identified, picked up using a tiny pipette and carefully injected directly into the cytoplasm (centre) of each mature egg. The fertilised embryos are allowed to develop as for standard IVF prior to transfer.

With ICSI, very few sperm are required and this process involves the direct penetration of the sperm into the egg. It is therefore recommended:

  • When the sperm count is very low
  • When the sperm cannot move properly or are in other ways abnormal
  • When sperm has been surgically retrieved directly from either the epididymis (the coiled tubing outside the testicles which store sperm) or testicle itself
  • When there are high levels of antibodies in the semen that can affect fertilisation
  • When there have been previous low fertilisation or fertilisation failures
  • When there is a high level of sperm DNA damage

Read more about the sperm COMET test

As ICSI bypasses the potential benefit of natural selection seen in IVF where thousands of sperm are left to attempt to fertilise an egg in the right conditions, we do not believe that ICSI should be the treatment of choice unless one of the above criteria are met.

Rarely after collection there are no mature eggs available for injection and a small percentage of eggs (<10%) may be damaged by the injection process and will no longer be viable. However, in both of these scenarios intrinsic egg quality is likely to be the main problem rather than the ICSI process itself. Whilst ICSI maximized chances of successful fertilisation in those with severe male factor fertility, there is still a 1-3% risk of couples failing to achieve any fertilised eggs.

Intracytoplasmic Morphological Sperm Injection (IMSI)

IMSI is a modification of the ICSI technique where sperm samples are examined under a microscope that is almost 6000 times more powerful to better assess their "morphology". At a higher power the embryologist can identify tiny defects in the sperm head that would not otherwise be visible with standard ICSI.

Although it is yet to be confirmed to be of benefit for all requiring sperm injection, it is recommended in those with a history of recurrent implantation failures, recurrent ICSI failures or severe teratospermia (abnormal sperm shape).

In essence it is a selection tool, to aid embryologists choose the optimal sperm for ICSI. If the sperm count or motility is already so low that it limits the number of sperm available for ICSI, IMSI may not be a suitable technique for you.

Are there any risks?
IMSI is a non-invasive test performed on a semen sample as an additional step in the ICSI process. The risks associated with the use of ICSI also apply to IMSI; there are no significant additional risks to the patient or embryo.

What's the evidence for IMSI?
There have been several RCTs within the last decade. Systematic reviews suggest that IMSI could be beneficial in specific situations such as previously failed ICSI attempts. The research that has been carried out does not support the use of IMSI over standard ICSI for infertile men. One small study found that IMSI had improved pregnancy outcomes in older women, however this study was carried out with a small number of women and the link, if any, between IMSI and older eggs is not fully understood.

Lister Fertility Clinic's opinion on IMSI

This is a modification of the standard ICSI procedure and one of a number of sperm selection techniques that have been suggested to potentially improve outcome. The major difference between IMSI and ICSI is that a higher magnification is used to assess sperm morphology allowing the embryologist to identify tiny defects in the sperm head that would not otherwise be visible with standard ICSI.

Reviews of randomized trials have shown a benefit in pregnancy but not livebirth rates so it cannot be justified in routine practice (Cochrane, 2013).
However, other trials of lower quality have suggested benefit over standard ICSI  in certain groups such as those with previous failed ICSI cycles (Klement et al, 2013 Fertil Steril), significant male fertility (Balaban et al, 2011 RBMO), those undergoing PGS (Figeira et al, 2011) and in the selection of sperm with lower levels of sperm DNA damage (Hammoud et al, 2012 Andrologia).

We therefore use in selected cases such as those above.

Download our information leaflet on the IMSI technique

The HFEA "traffic light rating" for IMSI is "red", suggesting that there is no good evidence to show that it is effective for routine use.

Read more about the HFEA traffic light system on fertility "add ons".

A fertility "add-on" is an "optional extras that you may be offered on top of your normal fertility treatment, often at an additional cost. They’re typically emerging techniques that may have shown some promising results in initial studies but haven’t necessarily been proven to improve pregnancy or birth rates".

Our fertility consultants

We're proud to work with leading fertility experts across a range of medical fields, including gynaecology and urology. 

Our team of consultants is supported by embryologists, sonographers and counsellors, as well as experienced fertility trained nurse practitioners.

Paying for medical treatment

You don’t need health insurance to have fast access to our top consultants, extensive range of treatments, diagnostic tests and surgical procedures at our world-class facilities.

Our locations

From complex fertility treatment and surgery to diagnostic tests and scans, we provide access to exceptional fertility and reproductive care across our network of fertility clinics.

Contact us about having fertility treatment

Our helpline advisors can assist with enquiries and help book an appointment with a fertility specialist. Alternatively you can submit a request for an appointment at one of our fertility clinics.


Request an appointment at Lister Fertility Clinic, Chelsea

Request an appointment at Lister Fertility Clinic, The Portland Hospital

Enquiries & Appointments

020 7881 2000
This content is intended for general information only and does not replace the need for personal advice from a qualified health professional.
back to top