ICSI or conventional IVF: when microinjection is truly beneficial

In the quotes I see, the line ‘ICSI’ almost always appears. Some patients aren’t even aware that another technique exists. It’s worth understanding the difference, because it comes at a cost, and because it doesn’t address the same issue.

Two ways of bringing an egg and a sperm together

In conventional IVF, each egg is placed in a drop of culture medium containing several tens of thousands of prepared sperm. Fertilisation occurs ‘naturally’: a single sperm penetrates the egg’s membranes on its own.

In ICSI (intracytoplasmic sperm injection), the embryologist selects a sperm under a microscope, immobilises it and injects it directly into the egg using a micropipette. This bypasses all the stages that the sperm would normally have to go through on its own.

In both cases, the subsequent steps are the same: embryo culture, transfer and, if necessary, freezing. ICSI does not ‘produce’ better embryos; it increases the chances of fertilisation occurring when there is a risk of it failing.

When ICSI is clearly indicated

• Significant male infertility: severely impaired concentration, motility or morphology on a semen analysis.
• Sperm retrieved surgically (TESE, micro-TESE) in cases of azoospermia: there are too few sperm for conventional IVF.
• Failure of fertilisation or very low fertilisation rates during a previous conventional IVF cycle.
• Frozen eggs: vitrification hardens the zona pellucida, and most clinics perform ICSI after thawing.
• Pre-implantation genetic testing (PGT): ICSI prevents any sperm cells remaining attached to the egg from contaminating the analysis.

When there is no proven benefit

For couples without male factor infertility, randomised trials have not shown that ICSI increases the live birth rate compared with conventional IVF. A large trial published in The Lancet in 2021, conducted in Vietnam on over a thousand couples without male factor infertility, found no difference in birth rates. The European Society of Human Reproduction and Embryology (ESHRE) therefore does not recommend routine ICSI in the absence of a male factor.

Why, then, is it so widespread? Because it reduces the risk – rare but very distressing – of complete fertilisation failure, and because it simplifies laboratory procedures. For a patient who has travelled across Europe for a single cycle, this argument carries weight. It is open to debate, but it is not absurd.

And what about borderline cases?

When few eggs are expected — due to advanced age or low ovarian reserve — some clinics offer ICSI so as ‘not to waste any’. The data do not show a clear benefit, but the decision remains a medical one. One option that is sometimes used is the ‘split’ approach: some eggs are used in conventional IVF, others in ICSI. This is particularly relevant during a first cycle, to see how your gametes behave.

Variations: IMSI, PICSI

IMSI selects sperm under very high magnification; PICSI selects them based on their binding to hyaluronic acid. Neither has shown an improvement in birth rates when used routinely. The UK’s Human Fertilisation and Embryology Authority (HFEA) classifies PICSI as a technique with no proven benefit. If these are offered to you, ask why they are being suggested in your specific case, and at what cost.

Safety

ICSI has been practised for over thirty years. The vast majority of children conceived using this method are in good health. There has been a slight increase in certain abnormalities, but this appears to be linked primarily to underlying male infertility rather than to the technique itself. This is yet another reason not to use it unnecessarily, though there is no need to fear it when it is medically indicated.

What I recommend asking

1. Is ICSI included in the price or charged as an extra?
2. Why is it being offered in my case: male factor, frozen eggs, PGT, standard practice at the clinic?
3. What is your usual fertilisation rate for conventional IVF and ICSI?
4. Is a split possible during the first cycle?

A good clinic will answer these questions without hesitation. And if the answer is ‘we perform ICSI for everyone’, this isn’t necessarily a bad sign — it’s simply a policy, which you have the right to know about.

Frequently asked questions