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IMSI — High-Magnification Sperm Selection

A variant of ICSI in which the sperm is selected by morphology under very high magnification before injection.

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IMSI — High-Magnification Sperm Selection

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Timing and clinic visits

IMSI is performed during the laboratory stage of an IVF cycle and does not extend the cycle.

Risks and limitations

Every medical procedure has possible risks and limitations. Personal risks and alternatives should be discussed before consent.

Who may be assessed?

Severely abnormal sperm morphology (teratozoospermia)
A high sperm DNA fragmentation result
Lower-than-expected fertilisation in previous ICSI attempts
Couples with repeated implantation failure or early pregnancy loss where a male factor is also present
Other situations where the embryology team considers it appropriate after assessing the sperm

Treatment process

01
Assessment
The semen analysis and, where needed, a DNA fragmentation test are reviewed together with the woman's investigations. The option of IMSI is discussed at this stage.
02
Ovarian stimulation
The same as an IVF cycle: a medication period of usually 8–12 days with ultrasound monitoring.
03
Egg and sperm collection
Eggs are collected under brief anaesthesia; the semen sample is provided the same day.
04
High-magnification selection
The embryologist examines the sperm at up to 6000x magnification and selects those with the most regular head structure.
05
Injection and embryo monitoring
The selected sperm is injected into the egg; the embryos are monitored in the laboratory for several days.
06
Transfer and follow-up
A suitable embryo is transferred to the uterus; a pregnancy test follows about two weeks later.

**Clinical assessment**We begin by listening and reviewing previous results together.

Laboratory processEggs and sperm are followed by the laboratory team according to the selected protocol.

Frequently asked questions

How does IMSI differ from ICSI?

The only difference is the sperm selection step. In ICSI the sperm is chosen at around 400x magnification; in IMSI at up to 6000x, looking at fine details of the head structure. Every other step is the same.

Is IMSI recommended for everyone?

No. It is considered where there is a specific reason — severely abnormal morphology, high DNA fragmentation or poor fertilisation in earlier attempts. Without such a reason, standard ICSI is sufficient.

Does IMSI give better results?

Evidence of additional benefit is limited and varies between patient groups. We do not publish general rates; your doctor will explain what to expect in your case based on your tests.

Does it make the process longer?

No. The selection takes a few hours in the laboratory and does not change the overall length of the cycle.

Detailed information

IMSI is a variant of intracytoplasmic sperm injection (ICSI). The difference lies in the selection step: in standard ICSI the sperm is chosen at roughly 400x magnification, whereas in IMSI the embryologist examines it at up to 6000x, assessing fine details of the sperm head.

It is not a separate treatment but a sperm selection technique used during the laboratory stage of an IVF cycle. Stimulation, egg collection, embryo monitoring and transfer proceed exactly as in a standard IVF cycle.

When it is considered

IMSI is considered when sperm morphology is severely abnormal (teratozoospermia), when sperm DNA fragmentation is high, or when fertilisation or embryo development was weaker than expected in previous ICSI attempts. The decision is made jointly by the embryology team and the doctor, based on the semen analysis and any additional tests.

What you should know

Scientific evidence on whether IMSI offers additional benefit over standard ICSI is limited and varies between patient groups. For that reason it is recommended only where there is a specific indication, not for everyone. Factors such as the woman's age, egg quality and the condition of the uterus remain decisive for the outcome.

This page is general information and does not replace medical consultation. The method that suits you is determined only after examination and testing.