What is IMSI, how does it differ from ICSI, and does it raise pregnancy chances? ESHRE, Cochrane and HFEA assessments, risks and questions for your doctor.
IMSI (intracytoplasmic morphologically selected sperm injection) is an add-on laboratory practice in which sperm are examined under very high magnification and selected by their shape before microinjection (ICSI). A current assessment prepared for Europe does not recommend its routine clinical use. A review could not show a clear effect on live birth, and based a possible increase in clinical pregnancy on evidence of very low reliability. This does not mean that the practice is harmful; it means that the evidence supporting routine use is insufficient. You can talk with your doctor about whether it will be considered in your own situation.
Does IMSI take the place of ICSI?
In ICSI, a single selected sperm is injected into the egg. IMSI is not a separate method that replaces ICSI; it is a step added to the stage at which the sperm is selected. That is, IMSI is an add-on practice carried out on the semen sample and included within the ICSI process.
Which features of the sperm are looked at under high magnification?
Under high magnification the internal structure of the sperm head is examined in more detail. How this detailed image will be reflected in the treatment outcome is an assumption; to show a benefit, studies looking at outcomes such as live birth are needed.
In which situations can IMSI be considered?
IMSI can be brought up in situations such as a male factor and advanced age. In these situations, enough data have not been collected to show that the practice improves outcomes. The assessment in the United Kingdom is the same in infertility due to a male factor too, that is, it remains uncertain.
Is IMSI needed in every ICSI treatment?
The evidence we have does not show that IMSI is necessary for all ICSI patients; nor is it strong enough to distinguish which group of patients would benefit. For this reason, the practice being considered is a clinical preference rather than a proven necessity.
Does IMSI increase the likelihood of live birth and pregnancy?
A review team brought together the controlled studies comparing standard ICSI with ultra-high-magnification sperm selection. The difference between the two approaches in live birth remained uncertain. It was reported that clinical pregnancy might have been more common with IMSI, but the reliability of this result is very low and the true size of the difference is not known. The authors of the review take the view that the data available are enough neither to support IMSI nor to rule it out.
Why is IMSI not recommended for routine use?
The current assessment on this subject puts IMSI in the group "not recommended for routine clinical use". Its basis is a meta-analysis showing live birth similar to standard ICSI, and the fact that the method is time-consuming in the laboratory workflow. The regulator in the United Kingdom, for its part, found no medium- or high-quality evidence sufficient to classify effectiveness. This uncertain classification does not show that the practice does not work; it only expresses that an assessment could not be made.
Why do studies not give a definite answer?
In many controlled studies of the last decade, findings of benefit are few and the reliability of these findings is low. The researchers add that better-designed studies of sufficient size are awaited. The literature search of this review closed at the end of 2019; newer studies could change the picture.
Which risks continue when IMSI is chosen?
Because IMSI is a selection step within the ICSI workflow, the risks of ICSI also apply to IMSI. The current assessment on this subject states that there are no data on the safety of IMSI; the regulator in the United Kingdom has not identified any additional risk specific to IMSI. This is not an assurance for every individual.
Is an extra fee needed for IMSI?
Depending on the centre, an additional charge may be requested for IMSI. If a previous cycle was unsuccessful, you may have the worry "if I do not have it done, my chance will fall"; knowing that the evidence is uncertain can help you weigh this worry in a more balanced way.
Are IMSI and PICSI the same thing?
No. Both are add-on approaches to selecting sperm before ICSI, but the principles of selection are different: IMSI looks at shape under high magnification, whereas PICSI rests on the property of binding to hyaluronan. The level of evidence of these approaches is assessed separately; the state of evidence of one cannot be transferred to the other.
What questions can you ask your doctor?
- Why is IMSI being recommended to me?
- What difference do you expect in my sample compared with standard ICSI?
- Is there an additional charge for IMSI?
- How would my plan take shape if IMSI is not done?
- How is IMSI worded in the consent form?
Frequently Asked Questions
Does IMSI reduce the risk of miscarriage (pregnancy loss)?
In one review, the difference in miscarriage was found uncertain, and the reliability of this result is very low. It therefore cannot be said that IMSI reduces or increases the risk of miscarriage.
Does it affect the risk of congenital anomaly?
None of the studies included in this review reported congenital anomalies; for this reason no conclusion can be reached on this subject. That none was reported does not mean that there is no risk.
Does it work at an advanced age?
The current assessment on this subject reports that a single study with a low number of participants suggests that pregnancy outcomes might be better in older patients. This relationship is not well understood; a benefit at an advanced age cannot be inferred from a single study.
My doctor recommended it; if it is not done, is the treatment left incomplete?
IMSI is a selection step added to ICSI; not doing it does not remove ICSI itself. You can ask your doctor the reasoning for the recommendation, what it is expected to change in your sample and, if there is one, its additional charge.
Is it worth paying an extra fee?
For patients who bear the cost of treatment themselves, repeating standard cycles with the same budget may also be considered as an option instead of an add-on whose effect has not been proven. You can ask the centre about the price and scope before the procedure.
Can ICSI not be done if I do not have IMSI?
No. IMSI is a step added to the sperm selection stage of ICSI. Not using it does not remove ICSI itself.
Does a more detailed image under high magnification mean a better treatment outcome?
No. Detail in the image and treatment outcomes such as live birth are different things. The benefit has to be shown by studies that measure clinical outcomes.
Is IMSI definitely useful if there is a male factor?
This conclusion cannot be drawn. The assessment is uncertain in infertility due to a male factor too; there are not enough data to show that outcomes improve.
Does uncertainty in the difference in live birth mean IMSI is ineffective?
No. The data available are enough neither to support nor to rule out the method. Insufficient evidence to support routine use is not the same as ineffectiveness or harm being proven.
Can the possible increase in clinical pregnancy be interpreted as a definite benefit?
No. The reliability of the possible increase reported in the review is very low, and the true size of the difference is not known.
Do IMSI and PICSI use the same selection method?
No. IMSI uses shape under high magnification, while PICSI uses binding to hyaluronan. The evidence for one method cannot be transferred to the other.
Is the absence of an identified additional risk for IMSI a safety guarantee?
No. Even though the regulator has not identified an additional risk, the other assessment states that there are no data on safety. The risks of ICSI continue, and no assurance can be given for every individual.
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