IMSI Sperm Selection: Advanced ICSI Technology for Male Infertility

In short: IMSI is the injection of a sperm chosen for its shape after it has been magnified 6,600–8,000 times, so that the best sperm are selected for ICSI. It is used when sperm are abnormal in shape or movement or after repeated ICSI failure. The embryologist needs about two to two and a half hours to examine the sample.

When couples face infertility linked to sperm quality, every detail matters. Research shows that only a small percentage of sperm cells have an entirely normal shape. At Dr. Layyous clinic, our embryology team works to select the healthiest-looking sperm possible, because we believe giving your embryos the best possible start matters.

Intracytoplasmic Morphologically Selected Sperm Injection, or IMSI, is an advanced laboratory technique developed to support couples affected by male factor infertility. It involves carefully examining sperm under very high magnification — around 6600 to 8000 times — to help embryologists choose sperm with the best visible structure before injection into the egg. This is a step beyond conventional ICSI, where sperm are typically viewed at 200 to 400 times magnification.

At this much higher magnification, embryologists can look more closely at the sperm head shape, size, and internal structure, including features that may be associated with higher DNA fragmentation — details that are difficult to see under a standard ICSI microscope. The goal of IMSI is to help the embryology team identify sperm with the most favorable morphology for injection, which may support embryo development.

It is important to know that large reviews of the research (Cochrane 2020) and the European Society of Human Reproduction and Embryology (ESHRE 2023) have not shown that IMSI increases the chance of a live birth for most couples, so it is not recommended routinely. It may be considered in selected cases — for example, severe teratozoospermia or repeated unexplained ICSI failure — after discussing the limited evidence with your doctor.

Because this process requires such careful, detailed observation, our embryologists may spend around two and a half hours reviewing sperm samples to identify the best candidates — time invested toward giving you the strongest possible chance in your treatment cycle.

Sperm selection under IMSI is guided by what is known as the Vanderzwalmen classification, a set of criteria describing normal sperm shape. According to this standard, sperm with good morphology are more likely to carry normal chromosomes and less fragmented DNA — both of which can play a role in embryo quality, implantation, and healthy growth.

Studies suggest that sperm selected using these stricter criteria may show better mitochondrial function, healthier chromatin structure, and lower rates of chromosomal abnormality, which may contribute to improved outcomes compared with conventional ICSI in some cases.

A normally shaped sperm nucleus is typically smooth, symmetric, and oval. This assessment is informed by findings from scanning electron microscopy and relies on:

• High-power microscopy
• Single-cell examination
• Observation of only motile sperm cells
• Detailed evaluation of fine organelle morphology

Potential benefits associated with IMSI

• Possibly fewer embryos affected by early developmental arrest in some couples, based on small studies
• Some studies have reported improved implantation and pregnancy rates, although higher-quality trials have not confirmed a higher live birth rate
• A possible option to consider after repeated ICSI cycles that were not successful
• Considered for patients with male infertility and high teratozoospermia (an increased proportion of abnormally shaped sperm)

If you have experienced difficulties with male factor infertility or previous ICSI cycles and would like to learn whether IMSI may be a suitable option for your situation, our team at Dr. Layyous clinic is here to answer your questions and guide you through your options.

What extended culture involves is explained in our page on day-5 blastocyst culture.

Dr Najeeb Layyous F.R.C.O.G

Consultant Obstetrician, Gynecologist and Infertility Specialist