ICSI vs Conventional IVF: What Changes in the Lab and Who Is Offered Each Method

The consent form arrives with a checkbox you did not expect. Above the signature line it asks whether you agree to “conventional insemination” or “ICSI” for your eggs, and the nurse mentions, kindly and in passing, that the lab will make a recommendation once the semen sample is assessed on the day. You nod. Then you go home and type the icsi vs ivf difference into your phone at eleven at night, because a decision about how your embryos are made feels too large to leave to a checkbox.

It is a reasonable instinct. The two methods share nearly every step, yet they part ways at the single most consequential moment of the whole process: the instant a sperm meets an egg. One approach lets that meeting happen on its own in a dish. The other has a trained pair of hands make it happen, one egg at a time, under a microscope.

Which is right for you depends less on which sounds more advanced and more on what your test results actually show. Here is what changes in the lab, who tends to be offered each method, and where the evidence is honest about its own limits.

ICSI vs IVF difference: the two-minute version

IVF, or in vitro fertilization, means an egg is fertilized by sperm outside the body, in a laboratory dish. ICSI, short for intracytoplasmic sperm injection, is a variation of IVF in which an embryologist (the laboratory scientist who handles eggs, sperm and embryos) injects one sperm directly into one egg. Every ICSI cycle is an IVF cycle; the reverse is not true.

Think of the difference as the last hundred yards of a long journey. Ovarian stimulation, monitoring scans, the trigger injection, egg retrieval, embryo culture, transfer and the two-week wait are the same whichever box is ticked. What changes is a few hours on the afternoon of retrieval. In conventional IVF the eggs and prepared sperm are simply placed together and left overnight. In ICSI each mature egg is stripped of its surrounding cells, held steady with a glass pipette, and pierced with a needle finer than a human hair carrying a single sperm.

Why would anyone choose the more invasive route? Because conventional insemination relies on sperm being able to swim to the egg, bind to its outer coat and push through it. When sperm are too few, too slow or too abnormally shaped to manage that, ICSI bypasses the problem entirely. The Cleveland Clinic describes this as the core purpose of the technique: it was developed for men whose sperm cannot fertilize an egg on their own.

The honest headline is this. For couples with a clear sperm problem, ICSI can turn a cycle that would likely produce no embryos into one that does. For couples without a sperm problem, the best available evidence has not shown that ICSI produces more babies than letting fertilization happen naturally in the dish, a point the rest of this article returns to.

What actually happens in the lab during conventional IVF

Egg retrieval usually takes place 34 to 36 hours after the final “trigger” injection that matures the eggs, according to Mayo Clinic, and the procedure itself takes around 15 to 20 minutes under sedation, per the NHS. A needle guided by ultrasound passes through the vaginal wall into each follicle, the fluid-filled sac that holds an egg, and the fluid is handed through a hatch to the embryologist.

Under a microscope, each egg arrives wrapped in a fluffy cloud of cumulus cells, the nurse cells that fed it inside the ovary. In conventional IVF those cells are left in place. They matter: they help guide sperm toward the egg and may help select healthy ones.

Meanwhile the semen sample is “washed.” That means it is spun in a centrifuge and layered through a density gradient so that motile, normally shaped sperm are separated from seminal fluid, debris and immotile cells. The result is a small, concentrated drop of the most capable swimmers.

Late in the afternoon, each egg is placed in a droplet of culture medium with a measured number of these sperm, typically tens of thousands. Then the dish goes into an incubator that mimics the body’s temperature and gas mix, and the lights go off. Fertilization, if it happens, happens unwatched.

The NHS notes that eggs and sperm are cultured together for around 16 to 20 hours before the embryologist checks for signs of fertilization: two small structures called pronuclei, one carrying the egg’s chromosomes and one the sperm’s, sitting side by side. From this point onward, an embryo made by conventional IVF and one made by ICSI are cultured, graded, transferred or frozen in exactly the same way.

How ICSI works: one sperm, one egg, one very fine needle

The ICSI afternoon begins differently. Because the embryologist must see the egg clearly and confirm it is mature, the cumulus cells are gently removed with an enzyme and fine pipetting. A mature egg shows a small structure called the first polar body, a cast-off packet of chromosomes that signals the egg has finished its final division and is ready to be fertilized. Immature eggs cannot be injected and are usually set aside.

Under a high-powered inverted microscope fitted with micromanipulators, joystick-controlled arms that translate hand movements into movements of a few thousandths of a millimeter, the embryologist holds the egg with a blunt suction pipette. With the other arm, they select a single sperm from the prepared sample, favoring one that looks normal and is moving. The sperm’s tail is pressed against the dish to immobilize it, a step that also helps trigger the egg’s activation later.

Then the injection: a glass needle carrying the sperm passes through the zona pellucida (the egg’s protective outer shell), through the egg’s membrane and into the cytoplasm, the jelly-like interior. The sperm is released and the needle withdrawn. Each egg takes a matter of minutes; a cohort of a dozen eggs occupies a good part of an hour.

The injected eggs then go back into the incubator, and the fertilization check the next morning looks identical to conventional IVF. What ICSI does not do is guarantee that a sperm placed inside an egg will fertilize it. The Cleveland Clinic notes that ICSI fertilizes roughly 50% to 80% of injected eggs; the egg still has to “wake up,” release its own chemistry and unpack the sperm’s DNA, a biological sequence no needle can force.

Who is usually offered ICSI, and who is usually asked to wait

Guideline-level practice across the NHS, Mayo Clinic and Cleveland Clinic points to a consistent shortlist of situations where ICSI is the standard offer:

• Severe male-factor infertility: very low sperm count, very poor motility (movement) or a high proportion of abnormally shaped sperm on repeated semen analysis.
• Sperm obtained surgically from the testicle or epididymis, for example after vasectomy or when no sperm appear in the ejaculate. These sperm are too few and often too immature to fertilize in a dish.
• A previous conventional IVF cycle in which few or no eggs fertilized despite apparently normal sperm.
• Eggs that were previously frozen, because freezing can harden the zona pellucida and make natural penetration less reliable.
• Cycles in which embryos will undergo preimplantation genetic testing (PGT), a biopsy of a few embryo cells to check chromosomes or a specific gene. ICSI avoids stray sperm clinging to the egg’s shell contaminating the genetic sample.

Who is usually asked to wait, or offered conventional insemination first? Couples with unexplained infertility, blocked fallopian tubes, endometriosis, ovulation disorders or advanced maternal age and a normal semen analysis. In these groups, professional society guidance and randomized trials have not found that ICSI improves the chance of a live birth compared with conventional IVF. The sperm can already do the job; adding a needle adds cost, labor and a small handling risk without adding benefit.

Many laboratories also use a middle path called “split” insemination for borderline cases: half the eggs are inseminated conventionally and half are injected. It is a way of learning, within one cycle, whether the sperm can fertilize unaided, while hedging against the risk of no embryos at all. Whether a split is sensible depends on egg numbers and the specific semen findings, and it is a decision for the embryology team and the treating physician together.

Is ICSI better than IVF? What the evidence actually shows

“Better” is the wrong frame, and it pays to be clear about why. ICSI and conventional IVF are not competing treatments for the same problem; they are two ways of achieving fertilization, each suited to a different biology.

Where the sperm cannot fertilize on their own, ICSI is unambiguously the more effective method, because the alternative is very often total fertilization failure. That is not a marginal gain; it is the difference between having embryos and not having them. Mayo Clinic lists poor semen quality and previous failed fertilization as the situations where ICSI is typically used, and no mainstream body disputes that.

Where the sperm are normal, the picture reverses. Randomized trials comparing ICSI with conventional insemination in couples without male-factor infertility have consistently failed to show higher live birth rates with ICSI. Fertilization rates per egg are sometimes a little higher with ICSI, but that advantage does not carry through to more good-quality embryos or more babies, and it is offset by the loss of some eggs to injection damage and the exclusion of immature eggs that occasionally would have matured and fertilized in a dish.

Despite this, CDC surveillance of assisted reproduction shows ICSI is used in a majority of cycles in the United States, far more than the proportion of couples with a male-factor diagnosis. Some of that reflects laboratories preferring the predictability of ICSI, some reflects patients asking for what sounds like the stronger option, and some reflects fear of an empty dish on day one.

The evidence-based position, then, is not that one method wins. It is that the method should follow the diagnosis, and that using ICSI “just in case” for couples who do not need it has not been shown to help them.

ICSI vs conventional IVF at a glance

The table below sets the two methods side by side. It describes what typically happens in most laboratories, not a promise about any individual cycle; protocols vary and your embryology team will explain their own.

Step	Conventional IVF	ICSI
Ovarian stimulation and monitoring	Same	Same
Egg retrieval	Same, about 34–36 hours after trigger (Mayo Clinic)	Same
Egg preparation	Cumulus cells left in place	Cumulus cells removed; only mature eggs used
Sperm preparation	Washed and concentrated	Washed; one sperm selected per egg
How fertilization occurs	Sperm swims to and penetrates egg unaided	Embryologist injects one sperm into egg
Sperm needed	Tens of thousands of motile sperm per egg	One viable sperm per egg
Natural sperm selection	Preserved	Replaced by embryologist’s visual choice
Fertilization check	About 16–20 hours later (NHS)	Same
Usual indication	Normal semen analysis	Male-factor infertility, prior failed fertilization, frozen eggs, PGT
Main procedural risk	Total fertilization failure if sperm underperform	Injury to a small proportion of eggs during injection
Embryo culture, transfer, freezing	Same	Same

Two rows deserve a second look. “Natural sperm selection” is the one thing conventional IVF preserves and ICSI removes: in a dish, only sperm capable of swimming, binding and penetrating get through, a crude but biological filter. “Sperm needed” is the row that explains ICSI’s existence: a man with a handful of viable sperm can become a genetic father, which before the early 1990s was simply not possible.

Eggs not fertilizing with ICSI: why it happens

It is one of the most unsettling phone calls in fertility treatment: the eggs were injected, and few or none fertilized. Patients often assume that ICSI, having placed the sperm inside, should make fertilization close to certain. It does not, and the reasons are instructive.

The most common explanation is failed oocyte activation. When a sperm normally enters an egg, it delivers a protein that triggers waves of calcium release inside the egg, and those waves are the “on switch” for everything that follows: completing the egg’s final division, forming the pronuclei, unpacking the sperm’s DNA. Some sperm carry too little of this activating protein, and some eggs respond weakly regardless of the sperm. Injection places the sperm in the right room but cannot flip the switch for it.

Egg quality is the second factor. Eggs that look mature can still have subtle abnormalities in their cytoplasm or their spindle, the structure that organizes chromosomes. These are more frequent with increasing age and in some ovarian conditions, and they lead either to no fertilization or to fertilization that stalls within a day.

Sperm DNA integrity plays a role too. A sperm that moves and looks normal may still carry fragmented DNA; the egg may attempt repair and fail, producing an arrested embryo rather than no fertilization at all.

Finally, a small proportion of eggs degenerate during the injection itself, which the Cleveland Clinic lists as a recognized risk of the technique.

When fertilization fails after ICSI, the laboratory’s report usually distinguishes these patterns, and the treating team may discuss further testing or, in selected cases, artificial oocyte activation, a laboratory step using a calcium-based medium to mimic the sperm’s signal. That approach is used in some centers for repeated failure, but it remains an add-on with limited high-quality evidence and is a decision for your specialist, not a standard step.

What are the potential disadvantages of ICSI?

A method that overrides one of biology’s oldest filters deserves a frank account of its downsides. None of these is a reason to refuse ICSI when it is indicated; all of them are reasons not to request it when it is not.

Egg damage comes first. The injection needle pierces the egg’s membrane, and a small proportion of eggs do not survive the puncture. For a woman with fifteen eggs this is a footnote; for a woman with three, losing one to the needle is a real cost.

Loss of natural selection is the subtler concern. In a dish, sperm must swim, bind to the zona pellucida and penetrate it, a sequence that tends to exclude many abnormal sperm. In ICSI the embryologist selects by appearance and movement at a few hundred times magnification, which cannot reveal DNA quality or chromosomal content. Whether this matters for the health of children is discussed below; the point here is that ICSI substitutes a human judgment for a biological one.

Immature eggs are excluded. Conventional insemination leaves cumulus cells in place, and occasionally an egg that was not quite mature at retrieval finishes maturing overnight and fertilizes. ICSI strips those cells to assess maturity and does not inject immature eggs, so a few potential embryos are forgone.

Safety questions remain partly open. Cleveland Clinic and Mayo Clinic both note a slightly higher rate of certain birth defects after assisted reproduction generally, and researchers still cannot fully separate the effect of the technique from the effect of the underlying infertility, particularly severe male-factor infertility that may itself carry genetic causes.

Lastly, there is the practical weight: ICSI is more labor-intensive, requires specialized equipment and highly trained staff, and adds a step at which human error, though rare, is possible. Laboratories mitigate this with witnessing systems, but the step exists.

ICSI for male infertility, frozen eggs and genetic testing: the special situations

Three scenarios make ICSI close to non-negotiable, and each illustrates something different about why the technique exists.

The first is severe male infertility, ICSI’s original purpose. When a semen analysis shows very few sperm, or sperm that barely move, conventional insemination is likely to fail. Where no sperm appear in the ejaculate at all, a condition called azoospermia, a urologist may retrieve sperm directly from the testicle or epididymis under anesthesia. Those sperm are typically few in number and immature in their swimming ability, and only ICSI can use them. The NHS lists sperm obtained this way as a standard reason for ICSI. Where azoospermia has a genetic cause, the treating team will usually recommend genetic counseling before proceeding, because some causes can be passed to sons.

The second is eggs that have been frozen and thawed, whether for planned fertility preservation, after cancer treatment, or from an egg donor bank. Freezing changes the zona pellucida, making it stiffer and harder for sperm to penetrate, and the cumulus cells are removed before freezing anyway. Nearly all laboratories therefore inject thawed eggs, even when the sperm are entirely normal.

The third is preimplantation genetic testing. When a few cells are biopsied from an embryo to check its chromosomes or screen for an inherited condition, any extra sperm still stuck to the embryo’s outer shell could contaminate the sample and produce a misleading result. ICSI, which exposes each egg to exactly one sperm, removes that risk. Some laboratories are now revisiting this rule for chromosome screening alone, but ICSI remains routine practice where genetic testing is planned.

Notice what these three situations share: a specific mechanical or analytical reason the sperm cannot, or should not, be left to find the egg on their own. Absent such a reason, the default in evidence-based practice remains conventional insemination.

What the following days and weeks usually look like

Whichever method was used, the calendar after retrieval runs the same course. The NHS estimates that a full IVF cycle, from the start of stimulation to the pregnancy test, takes around four to six weeks; the laboratory phase occupies less than one of those.

Day zero is retrieval and insemination or injection. Most people go home the same afternoon, feeling bloated, crampy and tired from the sedation, and are advised to rest.

Day one brings the fertilization call, usually mid-morning, after the 16-to-20-hour check the NHS describes. The number you hear is the number of eggs showing two pronuclei. It is normal for this to be lower than the number of eggs retrieved: not every egg is mature, and not every mature egg fertilizes, by either method.

Days two to five are culture. Embryos divide, and the embryologist grades them by cell number, symmetry and fragmentation. By day five or six a healthy embryo becomes a blastocyst, a hollow ball of about a hundred cells with a distinct inner group destined to become the fetus. Not every fertilized egg reaches this stage, and attrition here is biology rather than a sign of a laboratory problem.

Transfer, according to Mayo Clinic, usually happens two to five days after retrieval, placing one embryo (occasionally two) into the uterus through a fine catheter, a procedure that feels much like a smear test. Alternatively, all embryos may be frozen for a later transfer, a common choice when the ovaries need time to settle after stimulation.

Then the wait. The NHS advises a pregnancy test around two weeks after transfer. Spotting, cramping and mood swings during this window are common and are not reliable signs of either outcome. Your team will tell you how to reach them during these weeks and what symptoms warrant a same-day call.

Does ICSI affect the health of the baby?

Parents ask this in a low voice, as though the question itself were disloyal. It is not. It is the most important question in the field, and the honest answer has several layers.

Children conceived through assisted reproduction as a whole show a small increase in certain birth defects compared with children conceived naturally, a finding noted by both Mayo Clinic and Cleveland Clinic. The absolute increase is modest, meaning the great majority of children are born healthy, but it is consistent across large registries.

The harder question is how much of that increase belongs to the technique and how much to the parents’ underlying infertility. Couples who need ICSI often have severe male-factor infertility, and some causes of very poor sperm production are themselves genetic. When a sperm that could never have fertilized an egg naturally is used to make an embryo, any genetic contribution it carries is passed on. Studies comparing ICSI with conventional IVF in couples who did not have male-factor infertility tend to find little difference in outcomes between the two methods, which supports the idea that the sperm’s origin, more than the needle, explains most of the observed risk.

Specific concerns have been raised about a small increase in genital and urinary tract abnormalities in boys and in sex-chromosome variations after ICSI for severe male infertility. Follow-up studies of the first generation of ICSI-conceived adults have been broadly reassuring about growth, general health and development, while reporting that some sons of men with very low sperm counts have lower sperm counts themselves.

What this means in practice: where ICSI is medically indicated, its benefits are widely judged to outweigh these small risks; where it is not indicated, avoiding an unnecessary intervention is sensible. Genetic counseling before treatment, particularly for azoospermia, is standard and worth accepting.

What people often get wrong about ICSI and IVF

“ICSI is the upgraded version of IVF.” It is a targeted tool, not a newer model. For couples with normal sperm, trials have not shown more babies with ICSI. Requesting it as an upgrade adds a handling risk to your eggs without a proven return.

“With ICSI, fertilization is basically guaranteed.” The Cleveland Clinic puts ICSI fertilization at roughly 50% to 80% of injected eggs. The egg still has to activate; the sperm still has to have intact DNA. A needle changes the odds for men whose sperm cannot reach the egg, not the fundamental biology afterward.

“ICSI means the embryologist picks the best sperm.” Selection is by what is visible at a few hundred times magnification: shape and movement. That is a coarser filter than the egg’s own, which tests a sperm’s ability to swim, bind and penetrate. Whether visual selection is worse, better or neutral for embryo quality is unsettled.

“ICSI gives you more girls” (or boys). Some large registry analyses report a slightly lower proportion of male births after ICSI and a slightly higher one after conventional IVF; others find no difference. If a shift exists, it is small, inconsistent, and nobody should choose a method expecting to influence sex. Sex selection for non-medical reasons is also prohibited in many jurisdictions.

“ICSI is more painful or takes longer for the patient.” Everything the patient experiences is identical. The extra work happens in the lab, on the eggs, in the hours after retrieval.

“If fertilization failed once, the eggs were bad.” Failed fertilization can originate from the egg, the sperm or the interaction between them. The embryology report after a failed cycle usually points toward the more likely side, and that shapes whether ICSI, further sperm testing or a different stimulation approach is discussed next.

Questions to ask your care team

Arrive at your planning appointment with these written down. A good team will welcome them, and the answers will tell you as much about the laboratory’s reasoning as about your own case.

• Based on my semen analysis and history, do you recommend conventional insemination, ICSI or a split, and what specific finding drives that recommendation?
• If the recommendation is ICSI and there is no male-factor diagnosis, what evidence supports using it in my situation?
• Will the final decision be made before retrieval or on the day, once the fresh sample is assessed? Who makes that call, and will I be told before the eggs are handled?
• What is your laboratory’s typical fertilization rate per mature egg with each method, and how do those compare with published ranges?
• How many of my eggs might be lost to injection damage, and how does that weigh against the risk of no fertilization if we use conventional IVF?
• If few or no eggs fertilize, how quickly will I hear, and what would you propose for a future cycle?
• Do you offer rescue ICSI, injecting eggs the next morning if conventional insemination has failed, and what does the evidence say about embryos made that way?
• Is preimplantation genetic testing planned, and does that make ICSI necessary in your laboratory?
• For surgically retrieved sperm or azoospermia, is genetic counseling part of the pathway before we proceed?
• What witnessing or double-checking systems does the lab use to confirm the right sperm and eggs are matched?
• Which of my symptoms after retrieval or transfer should prompt a same-day call, and how do I reach someone out of hours?

Notice that none of these questions asks the team to promise an outcome. They ask for the reasoning behind a recommendation, and reasoning is what you are entitled to.

When to call your doctor

The laboratory method makes no difference to the physical warning signs after treatment; these belong to ovarian stimulation, egg retrieval and early pregnancy, whichever way the embryos were made. The NHS and Mayo Clinic describe the most important complication as ovarian hyperstimulation syndrome (OHSS), in which the stimulated ovaries swell and leak fluid into the abdomen, and both note that severe cases, though uncommon, can be dangerous.

Contact your fertility unit the same day, or attend an emergency department if you cannot reach them, for any of the following:

• Rapidly worsening abdominal swelling or a belly that feels tight and heavy within a few days of retrieval.
• Severe or steadily increasing pelvic or abdominal pain that simple measures suggested by your team do not ease.
• Vomiting that prevents you keeping fluids down, or passing much less urine than usual.
• Shortness of breath, chest pain or a persistent cough, which can signal fluid around the lungs or a blood clot.
• A swollen, painful or red calf or thigh.
• Fever, chills or foul-smelling vaginal discharge after retrieval or transfer, which may indicate infection.
• Heavy vaginal bleeding, soaking through a pad in an hour, at any point.
• Fainting, dizziness on standing or a racing heartbeat.
• After a positive test: one-sided pelvic pain, shoulder-tip pain or bleeding, which need urgent assessment to exclude an ectopic pregnancy, an embryo implanted outside the uterus.

Mild bloating, period-type cramps, breast tenderness, constipation and light spotting are common and usually expected; mention them at your next scheduled contact rather than worrying alone. Sudden emotional lows are also common in the weeks after transfer, and your team can point you to counseling support if they persist.

Every decision about the method used for your eggs, about further testing after a failed fertilization, and about how to manage any complication rests with your treating team, who know your history and your results. This article is a map of the territory, not a route.

Frequently asked questions

Which one is better, ICSI or IVF?

Neither is better in general; each suits a different problem. ICSI is the more effective method when sperm cannot fertilize an egg on their own, because the alternative is often no embryos at all. When semen analysis is normal, randomized trials have not shown that ICSI produces more live births than conventional insemination, and it removes the egg’s natural sperm selection while risking a few eggs during injection. The right method follows the diagnosis, and your treating team should explain which finding drives their recommendation.

Which gender is more likely with ICSI?

Any effect on sex ratio is small and inconsistent. Some large registry analyses report a slightly lower proportion of male births after ICSI and a slightly higher one after conventional IVF, while other studies find no difference. Researchers have proposed that culture conditions or the timing of fertilization might play a role, but nothing is settled. No one should choose a laboratory method expecting to influence a baby’s sex, and non-medical sex selection is prohibited in many countries.

What are the potential disadvantages of ICSI?

The main disadvantages are a small proportion of eggs damaged by the injection needle, the loss of the egg’s own biological sperm selection in favor of an embryologist’s visual choice, and the exclusion of immature eggs that occasionally would have fertilized in a dish. Mayo Clinic and Cleveland Clinic also note a slightly higher rate of certain birth defects after assisted reproduction, which may partly reflect the underlying infertility rather than the technique. It is also more labor-intensive and adds a human step where error, though rare, is possible.

Why do eggs not fertilize with ICSI?

Most often because the egg fails to activate. A sperm normally delivers a protein that triggers calcium waves inside the egg, switching on fertilization; some sperm carry too little of it, and some eggs respond weakly. Other causes include subtle egg abnormalities linked to age or ovarian conditions, sperm with fragmented DNA that the egg cannot repair, and degeneration of a few eggs from the injection itself. The Cleveland Clinic notes that ICSI fertilizes roughly 50% to 80% of injected eggs, so some non-fertilization is expected.

Is ICSI for male infertility only?

No, though male infertility remains its main indication. ICSI is also routinely used for eggs that were frozen and thawed, because freezing stiffens the egg’s outer shell; for sperm retrieved surgically from the testicle, which are too few and immature to fertilize in a dish; when embryos will undergo preimplantation genetic testing, to avoid stray sperm contaminating the sample; and after a previous cycle in which eggs failed to fertilize despite normal-looking sperm. In each case there is a specific mechanical or analytical reason.

Does ICSI hurt more or take longer than IVF?

Nothing changes for the patient. Stimulation, monitoring, the retrieval procedure, embryo culture, transfer and the two-week wait are identical whether eggs are inseminated conventionally or injected. The extra work of ICSI happens in the laboratory on the afternoon of retrieval, on the eggs rather than on you. The NHS estimates a full cycle at around four to six weeks for both approaches, with the pregnancy test about two weeks after transfer.

Can you switch from IVF to ICSI if the eggs do not fertilize?

Some laboratories offer “rescue ICSI,” injecting eggs the morning after conventional insemination has clearly failed. By then the eggs are a day older, and embryos made this way have shown lower development and pregnancy rates in many reports, so many centers instead advise a fresh cycle with ICSI planned from the start. Whether rescue ICSI is offered, and whether it makes sense for your egg numbers, is a decision for your embryology team and physician.

Does ICSI use fewer eggs than conventional IVF?

Slightly, in practice. Before injection the embryologist removes the surrounding cumulus cells to confirm each egg is mature, and only mature eggs are injected; immature ones are usually set aside. In conventional IVF those cells stay in place and an occasional egg that finishes maturing overnight may still fertilize. A small proportion of injected eggs also degenerate from the needle. For most people with a reasonable number of eggs the difference is minor, but it matters more when only a few eggs are retrieved.

Does ICSI increase the risk of birth defects?

Children born after assisted reproduction as a whole show a small increase in certain birth defects compared with natural conception, a point noted by Mayo Clinic and Cleveland Clinic. How much is due to ICSI itself is unclear, because couples who need ICSI often have severe male infertility that may have genetic causes carried by the sperm. Studies in couples without male-factor infertility find little difference between ICSI and conventional IVF, which suggests the sperm’s origin, more than the injection, explains most of the risk.

Why do so many clinics use ICSI if the evidence for routine use is weak?

CDC surveillance shows ICSI is used in a majority of assisted reproduction cycles in the United States, well above the share of couples with a male-factor diagnosis. Laboratories value its predictability, clinicians fear the distress of total fertilization failure, and patients often ask for what sounds like the stronger option. Professional guidance, however, has not found a live-birth benefit for couples with normal sperm. Ask your team which specific finding in your case justifies ICSI, and expect a clear answer.

References

• NHS: IVF: What happens
• NHS: IVF: Risks
• MedlinePlus: In vitro fertilization (IVF)

This article is for general information only and is not a substitute for professional medical advice. Please consult a qualified doctor about your individual situation.