"In this country, we don't believe that"

On changing your mind — and why I am in no hurry to make up mine about a new fertility device

There is a sentence I have never forgotten. Not because it wounded me, but because of what it taught me to watch for in myself.

Twelve years ago, newly arrived in England as a registrar, I was asked to present at the departmental teaching. I brought a paper I had published in Urology — one I had written from the first letter to the last, grown out of my own thesis. It asked a narrow question. When a man has a varicocele repaired — a varicocele being a knot of enlarged veins in the scrotum — can we tell in advance whose sperm will actually improve? We found that you could, from a particular pattern of backward blood flow visible on a scan before surgery. Age, which everyone assumed would matter, did not.

I never got to present it. Before the discussion could begin, a senior colleague said:

"In this country we do not believe that varicocele is associated with infertility."

And that was the end of it. Not a criticism of the method, not a question about the cohort.

I want to be careful here, because this is not a story about one man, and it is certainly not a story about a country. He was not being eccentric or unkind — he was stating the settled position, accurately. At that time the national guidance in this country did not support treating varicocele as a fertility intervention. He had read the evidence as his profession had read it, and he was passing it on faithfully. Most of us are doing that most of the time.

What was missing was not knowledge. It was a question.

What changed

And here is the part I find genuinely admirable, which is why I tell this story at all.

In 2026 NICE published its updated fertility guideline. It now says that radiological or surgical treatment should be considered for men with a varicocele who are trying to conceive naturally and who have reduced semen parameters.

An institution looked again at a position it had held for over a decade, and moved. That is not an embarrassment. That is the system working as it is supposed to, slowly and in public — and it is a great deal more than most of us manage privately.

That is, more or less, where the European Association of Urology and the American societies had been sitting for years. Treat the man whose varicocele can actually be felt on examination and whose semen test is abnormal — how many sperm there are, how well they move, how they are shaped. Not everyone. Not nobody.

I could tell that as a story about being right. It would be the wrong story, and much the less interesting one.

Look again at what my paper had actually argued. Not "varicocele causes infertility" — a slogan. It argued selection: here is a marker that tells you which men are likely to benefit. The reply I received was an absolute. What changed in 2026 was not that the absolute flipped from no to yes. It is that the absolute was replaced by a criterion. The guidance moved from a belief about varicocele to a question about this man.

That is the useful lesson, and it points straight back at me. A belief closes a conversation. A criterion opens one — because a criterion can be tested, argued with, and revised by whoever comes next.

Which brings me to ZyMōt

ZyMōt is a small device used in some IVF and ICSI laboratories to choose which sperm to use. (ICSI, intracytoplasmic sperm injection, means injecting one sperm directly into an egg rather than leaving egg and sperm to find each other in a dish.)

Instead of spinning the sample in a centrifuge, it makes the sperm swim through a very fine membrane. The ones that get through are the strongest swimmers — and, this is the point, they carry far less DNA damage: fewer breaks in the genetic material packed inside the sperm head.

It is offered by a number of UK clinics as an optional extra. The public UK price lists I checked put it at roughly £180–£250 on top of a cycle.

I have no commercial interest in it. I do not sell it, I do not supply it, and I do not run an IVF laboratory — the decision to use ZyMōt belongs to your fertility clinic and your embryologist, not to me. My own clinical work includes male-fertility surgery, including varicocele repair and surgical sperm retrieval, so I will be explicit about where evidence ends and clinical judgement begins. What I can do is tell you what the evidence does and does not show, so that the conversation you have with your clinic is a better one.

There are three things worth knowing, and they are not the same kind of thing.

Three things worth knowing

This is the strongest part of the evidence. In a blinded split-sample laboratory study published in Human Reproduction, semen samples from infertile men were processed both by conventional preparation and by microfluidic sorting. The microfluidic fraction came back with DNA fragmentation that was close to undetectable. Other microfluidic studies have reported similar sperm-DNA improvements, although devices, populations and laboratory methods are not identical.

That is a real bench effect in the cited work. It is the part I am most comfortable saying out loud.

Here I have to be honest rather than encouraging.

Reducing DNA fragmentation is a laboratory result. A baby is a clinical result, and the road between the two is longer than it looks. When you gather the trials together, the picture is genuinely unsettled. A 2023 systematic review and meta-analysis of microfluidic sperm selection found marginal clinical-pregnancy and miscarriage results, without statistical significance, and did not establish a live-birth advantage.

There is one small randomised study reporting a live-birth advantage, but it was from a single centre, has not been replicated, and tested a related microfluidic chip rather than ZyMōt itself. More recent ZyMōt and microfluidic studies are also mixed: one randomised sibling-oocyte study using ZyMōt Multi found higher fertilisation but no significant improvement in later embryo outcomes, and its authors state that larger trials are still needed to know whether this translates into live birth.

So the honest position is not "it doesn't work". It is: we don't yet know whether it helps you take a baby home, and anyone who tells you otherwise is running ahead of the evidence. That includes anyone selling it.

You should also know exactly what the regulator has, and has not, said. The HFEA — the UK fertility regulator — rates some IVF add-ons with a traffic-light system. Microfluidic sperm selection, including ZyMōt, is not currently on that rated list. The two nearest sperm-selection relatives that have been rated — PICSI and IMSI — sit at black ("no effect") and grey ("insufficient evidence"). The HFEA's separate page on sperm DNA damage is also cautious: it says the evidence is conflicting, depends on the test used, and that the result is unlikely to change treatment management.

In the studies and regulatory material I checked, I did not find a reported safety signal specific to ZyMōt or microfluidic sperm selection. That matters, but it must be phrased carefully. Many fertility add-on studies are designed mainly to measure effectiveness, not long-term safety in children, so "no reported signal" is not the same as "proved harmless".

One technical caveat that is rarely mentioned: because the device selects for the best swimmers, it recovers fewer moving sperm overall. If your count is normal this is irrelevant. If your count is low, it may not be — and that is a question for your embryologist about your own sample, not a general rule.

Which leaves cost. And here I will give you my opinion, clearly labelled as opinion, because the evidence does not decide it for you.

Where I land, and why it is a judgement and not a finding

The HFEA puts the average cost of one IVF cycle at around £5,000, while warning that extra appointments, storage and add-ons may increase the bill. Drugs are often separate too. So the only honest way to discuss cost is with an itemised treatment plan from the clinic in front of you.

The couple in front of me is often not choosing between ZyMōt and something else. They are choosing between doing this and not doing it, once, in a year when she may be working with the last eggs she has.

I want to name the argument against first, because it is a good one and I have not ignored it. Regulators are wary of cheap add-ons not because any single one is ruinous, but because they accumulate. Each is modest, each is plausible, each is offered with a shrug — and a fertility bill quietly grows by thousands, with no one step being the culprit. Benefit of the doubt is defensible only item by item, with a reason for each. It is not defensible as a general policy of saying yes.

Set £180–£250 against a cycle of that size — a few per cent of the treatment cost before drugs and extras — with no reported safety signal on one side and an unproven but biologically coherent benefit on the other, and the arithmetic stops being only about money. It becomes about which regret you could live with. I am not comfortable telling such a couple to decline something plausible and low in procedural burden in order to save a few per cent of what they are already spending.

So, with that caveat visible: I would often extend the benefit of the doubt.

What to ask your clinic

Not "should I have ZyMōt?" — they will hear that as a request. Ask instead:

Prior fertilisation failure, a high DNA fragmentation result, repeated implantation failure — these are situations where the clinical reasoning may be stronger, not settled UK indications. "We offer it to everyone" is a different answer, and you should hear it as one.

If the answer is fertilisation rate or embryo numbers, that is honest. If the answer is your chance of a baby, ask what that is based on.

This is a fair question. Your clinic should be able to explain the specific clinical reasoning for ZyMōt in your case, not just the general principle.

Microfluidic sorting recovers fewer total sperm because it selects for the best swimmers. If you start with a low count, this could matter. If your count is normal or high, it usually doesn't.

Frequently Asked Questions

No. ICSI is the technique — injecting one sperm directly into an egg. ZyMōt is one way clinics select which sperm to inject. You can have ICSI without ZyMōt, or ZyMōt with conventional IVF (not ICSI). They're separate decisions.

Because lab results don't always translate to clinical outcomes. Lower DNA fragmentation is measured and real, but we don't yet have robust evidence that it changes your chance of a live birth. It might, but we need larger, well-designed trials to know.

Not routinely. It's offered as a private add-on by some UK clinics. If you're having NHS-funded IVF, you'd need to pay extra for ZyMōt, or you'd need to access the full cycle privately.

That's a conversation for your embryologist about your sample. The device selects for the best swimmers, which can recover fewer total sperm. If your starting count is low, that might matter. If it's normal, it usually doesn't.

No reported safety signal has been identified in the studies and regulatory material I reviewed. However, long-term safety evidence in children born after microfluidic selection is limited — the data collection period has been relatively short. This is true for many fertility add-ons. Your clinic can discuss any specific concerns with you.

The short version

Key takeaway

We know microfluidic selection can recover sperm with lower measured DNA damage, and ZyMōt is one way clinics try to use that principle. We do not yet know whether that means more babies — the trials disagree, and it is not honest to pretend otherwise. I found no reported safety signal, but the long-term safety evidence is not the same thing as a guarantee.

Twelve years ago I was told what was believed. What I have learned since is that "we believe" and "we do not believe" are equally poor answers, and that the interesting question is always the next one: what would change my mind, and how would I know?

The guidance on varicocele changed because people kept asking that. I owe a device I rather like the idea of exactly the same treatment — curiosity, patience, and a clear statement of what evidence would move me. It is the least comfortable position to hold in public, and I think it is the only honest one.

Mr Giangiacomo Ollandini, Consultant Urological Surgeon & Andrologist.

I have no financial or commercial interest in ZyMōt or in sperm DNA fragmentation testing. My clinical practice includes male-fertility surgery, including varicocele repair and surgical sperm retrieval.

General information, not medical advice. Decisions about your IVF or ICSI cycle belong to you and your fertility clinic.