By Zaira Salvador BSc, MSc (embryologist).
Last Update: 07/20/2018

Intracytoplasmic Morphologically Selected Sperm Injection (IMSI) is an improved type of ICSI (Intracytoplasmic Sperm Injection), and both techniques are used in IVF cycles to increase the success rates.

Today, the IMSI procedure is used to improve the sperm selection process before it is injected into the egg cell.

This state-of-the-art technique has many benefits for men with teratoozospermia, especially in severe cases where most sperms are abnormally shaped.


The many improvements made in the field of Assisted Reproductive Technology (ART) have allowed improved and innovative techniques to be available for IVF patients, all of them developed to increase the success rates of fertility treatments.

IMSI, also known as Super-ICSI, is one of these cutting-edge technologies, which uses a special lens for the microscope, which enables an increase greater than 6300-fold of spermatozoa. This is a major advantage in comparison with ICSI, in which sperm are selected individually under a microscope at 400x magnification instead of 6000x.

In short, IMSI allows the embryologist to see the structure of spermatozoa in detail, thereby detecting potential abnormalities and defects in the head, middle-piece, and/or tail.

According to the World Health Organization (WHO), for a sperm cell to have an excellent morphology, it must have the following characteristics:

  • Oval head
  • Straight or uncoiled tail
  • Fixed nucleus
  • Transparent color

Moreover, the acrosome must be intact and not contain vacuoles.

Currently, the most widely used technique used in IVF cycles is ICSI, especially in cases of severe male infertility, or when the sperm count, motility, or morphology are affected.

However, ICSI is a subjective technique, as it is the specialist who chooses the sperms following his personal criteria when observing the head, middle-piece, and tail.

Thanks to IMSI and the improvements that it adds to the process of examining and selecting sperms, the pregnancy success rates can improve in cases of male infertility.

When we select the sperms with the best morphology only, we dismiss those with poor morphology, which doesn’t mean that they were unable to fertilize the egg. Poor morphology increases the risk of implantation failure and miscarriage, though.

When is it used?

Severe male infertility is one of the most common causes of male infertility. For example, a man has low sperm quality when the sperm count is poor, the sperms are too slow, or the sperm morphology is abnormal.

As for IMSI in particular, it is indicated when sperm morphology is altered, a disorder that is known as teratozoospermia or teratospermia.

Selecting sperms with a good or normal morphology increases the pregnancy success rates in patients with infertility.

Moreover, IMSI can be used in the following cases as well:

  • IVF/ICSI failure
  • Poor quality embryos that stop growing
  • Implantation failure
  • Severe oligoasthenoteratozoospermia
  • Severe sperm DNA fragmentation
  • Long-term unexplained infertility

It should be noted that IMSI is not used on a regular basis in IVF labs. It is used in very special cases only, as the cost is considerably high and it does not increase the success rates in all cases.

If you need to undergo IVF to become a mother, we recommend that you use "The Calculator". In 3 simple steps, it will show you a list of clinics that fit your preferences and meet our strict quality criteria. Moreover, you will receive a report via email with useful tips to visit a fertility clinic for the first time.

Benefits of IMSI

The main benefit of IMSI is that it allows for an accurate visualization of sperm cells, that is, an increase greater than 6300-fold of spermatozoa. To sum up, IMSI is 15 times more powerful than conventional microscopes used in IVF/ICSI cycles.

With IMSI, live sperms can be selected in real time. Thanks to it, dye tests that could damage the sperm cells become unnecessary to check sperm quality.

Visualizing the sperms in such detail not only allows us to detect potential head defect, but also in the middle-piece or neck, an the tail. The presence of such defects is associated with sperm DNA fragmentation.

The IMSI technique increases the fertilization and pregnancy rates, whilst decreasing the miscarriage rate.


In spite of all the advantages that IMSI can add to your fertility treatment, it also has some cons that one should consider, including:

  • It adds a considerable amount of extra time to the IVF procedure: about 1.5 to 5 hours.
  • Due to its elevated cost, it is not available in most IVF laboratories.

For all these reasons, IMSI is used only when sperm quality is too low or in cases of repeated IVF or IVF with ICSI failure.

More research is necessary as regards this technique in order to prove its clinical efficacy and determine the cases when it is actually required more accurately.

FAQs from users

Is IMSI possible with sluggish sperm?

By Zaira Salvador BSc, MSc (embryologist).

Yes, IMSI is possible with sperm samples that contain sluggish sperm, that is, samples with asthenozoospermia, as long as it is indicated for the reasons explained above.

The main purpose of IMSI is to select the sperm cells with the best morphology only. To select sperms with progressive motility, however, conventional ICSI is the technique of choice.

How does IMSI work?

By Zaira Salvador BSc, MSc (embryologist).

The IMSI procedure is the same as in ICSI cycles. First, the sperm sample is processed in the lab, and the pellet is resuspended at the adequate concentration. The only difference between IMSI and ICSI is the microscope used to select the sperms morphologically with IMSI. This type of microscope is based on the MSOME technology (Motile Sperm Organelle Morphology Examination), which is equipped with a digital imager.

Once the embryologist selects the best sperms, they are transferred to the ICSI plate and taken to a conventional microinjector to fertilize the eggs.

Why does IMSI take too many steps?

By Zaira Salvador BSc, MSc (embryologist).

Because it is a very laborious technique that can be conducted by highly trained professionals only. Oftentimes, it requires two embryologists to work simultaneously in order to reduce the duration of the process and perform it more objectively.

Moreover, due to the use of a more powerful microscope, finding sperm cells under the microscope becomes a tedious task, which turns it into a technically challenging technique.

Suggested for you

We have mentioned teratozoospermia as the main indication for IMSI to be used. To get a much deeper insight on this sperm disorder, we recommend that you visit the following post: What Is Teratozoospermia? – Causes, Pregnancy Rate & Treatment.

According to the WHO, a semen analysis is the most useful tool when it comes to evaluate male fertility, as it is used to detect potential sperm disorders. Learn more about it here: What Is a Semen Analysis Report? – Purpose, Preparation & Cost.

Today, ICSI is the most widely used technique in IVF labs. Get more info by clicking the following link: What Is ICSI Technique? – Process, Success Rates & Cost.

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Authors and contributors

 Zaira Salvador
BSc, MSc
Bachelor's Degree in Biotechnology from the Polytechnic University of Valencia (UPV). Embryologist specializing in Assisted Procreation, with a Master's Degree in Biotechnology of Human Assisted Reproduction from the University of Valencia (UV) and the Valencian Infertility Institute (IVI). More information
License: 3185-CV
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