ICSI (Intracytoplasmic Sperm Injection): How the Procedure Works
ICSI (Intracytoplasmic Sperm Injection) is the most widely used treatment for male-factor infertility and is often recommended when there are issues with sperm quality or fertilisation. In this guide, we’ll walk you through how it works, who it’s for, and what to consider before starting.
Author
Tassia O’Callaghan
Reviewed by
Kayleigh Hartigan
21 min read
Updated 19th August 2025
Treatment spotlight:
- ICSI is a specialised form of IVF where a single sperm is injected directly into an egg to help overcome sperm-related infertility, such as low count or poor motility. It’s especially useful when fertilisation is unlikely to happen with standard IVF. [1]
- ICSI is most often recommended when sperm quality is poor, sperm needs to be surgically retrieved, or previous IVF attempts failed due to low fertilisation. It’s also sometimes used for genetic testing to avoid contamination from extra sperm.
- ICSI is used in approximately 46% of all IVF cycles in the UK, with the rate increasing each year, according to HFEA data. [2]
- The ICSI process takes 4–6 weeks, including ovarian stimulation, egg collection, sperm retrieval, fertilisation, and embryo transfer — all similar to IVF, but with a different fertilisation technique in the lab.
- ICSI can improve fertilisation rates in IVF (about 73% vs 65% for IVF), but doesn’t guarantee pregnancy or live birth — overall success rates are comparable to IVF unless there’s a clear sperm issue. [3]
- Like all fertility treatments, ICSI carries risks, including a slightly higher chance of passing on male infertility, possible egg damage during injection, and a small increased risk of congenital conditions — though most ICSI babies are healthy. [4]
- ICSI is available on the NHS in certain cases, usually when there’s a diagnosed male fertility issue — but eligibility criteria (like age, BMI, and how long you’ve been trying) vary by location.
What is ICSI?
ICSI is intracytoplasmic sperm injection. It’s a specialised form of IVF where a single sperm is injected directly into an egg by an embryologist in the lab.
This technique helps overcome certain sperm-related issues — like low count, poor movement (motility), or abnormal shape — that can make it harder for fertilisation to happen naturally or with standard IVF. By placing the sperm inside the egg, ICSI bypasses any barriers the sperm might face on its own and gives fertilisation the best possible chance. [1]
The rest of the treatment follows the same process as IVF: eggs are collected after hormonal stimulation, fertilised in the lab, and then one or more embryos are transferred back into the uterus.
It’s worth knowing that while ICSI is technically a part of IVF (not a standalone treatment), many people — including clinics and community members — often refer to it simply as “ICSI.” This can be confusing if you’re reading or talking about treatment options, especially online. What’s really happening is an IVF cycle with ICSI used as the fertilisation method in the lab.
In fact, some heterosexual couples may go through an “ICSI cycle” specifically to overcome male-factor infertility — and may not always realise that the full IVF process is still involved, from hormone stimulation to egg collection and embryo transfer. If you see the term ICSI used on its own, just remember: it’s an add-on to IVF, not a separate treatment — but it’s commonly talked about as if it is.
Who is ICSI for?
ICSI is most commonly recommended for people whose fertility path involves sperm-related challenges. That could include:
- Heterosexual couples where the sperm provider has a fertility issue: ICSI is often used when sperm count, shape or movement make fertilisation more difficult.
- Couples who’ve had previous IVF with little or no fertilisation: If standard IVF hasn’t worked, ICSI can be a next step to improve fertilisation chances.
- People who’ve had a vasectomy or have a blockage preventing sperm release: Sperm may be surgically retrieved and used in ICSI to help create embryos.
- People using frozen sperm, especially if it was stored during medical treatment: Sperm quality can be affected by freezing, and ICSI helps give fertilisation the best chance.
- People having genetic testing on embryos (PGT): ICSI reduces the risk of extra sperm sticking to the eggs, which can affect test results.
- Single people or same-sex couples using a sperm provider with known fertility issues: ICSI may be used to maximise fertilisation from a known or tested sperm source.
Your doctor will talk you through whether ICSI is right for your situation and whether it gives you the best chance of success.
Before you start treatment, remember:
- ICSI is part of IVF. The full IVF process still applies — including hormone stimulation, egg collection, fertilisation in the lab, and embryo transfer.
- It doesn’t fix egg-related issues. If low or poor-quality eggs are the reason fertilisation hasn’t happened before, ICSI is unlikely to help.
- Your sperm may need to be surgically retrieved. This is usually done as a minor procedure under local anaesthetic, and your doctor will guide you through what’s involved.
- Success rates depend on multiple factors. While ICSI can improve fertilisation, pregnancy rates also depend on things like egg quality, uterine health, and age.
- ICSI isn’t always necessary. If there’s no evidence of sperm-related infertility, standard IVF may be just as effective — and less expensive.
- There are some risks, as with any treatment. Your doctor will explain the potential risks and side effects before you start.
Find the right clinic for you
Choosing a clinic is one of the biggest decisions you’ll make. We’ll find the best options for you and arrange your pre-treatment tests, empowering you from this point onwards.
ICSI: Step-by-step
Step 1: Pretreatment
Time: 2–6 weeks
Location: Home and clinic
Before treatment starts, you’ll have fertility assessments to confirm that ICSI is the right option. These may include blood tests, semen analysis, ultrasound scans, and a detailed consultation with your clinical team.
If you’re going ahead with ICSI, the next step is ovarian stimulation. You’ll take hormone injections daily for around 10–14 days to encourage your ovaries to produce multiple eggs. Your clinic will monitor your response with blood tests and scans, and they’ll let you know when you’re ready for egg collection. In some cases, people may also start taking supplements or make lifestyle adjustments before treatment to support egg and sperm quality.
Step 2: Egg collection
Time: 20–30 minutes (plus recovery time)
Location: Clinic
Once your hormone stimulation phase is complete, you’ll take a final ‘trigger’ injection to prepare your eggs for collection. This injection is carefully timed, and your clinic will tell you exactly when to take it — typically 36 hours before egg retrieval.
Egg collection is a minor surgical procedure carried out under sedation or light anaesthetic. Using ultrasound guidance, your doctor will gently retrieve the eggs from your ovaries using a thin needle. You’ll usually be at the clinic for a few hours on the day, and may feel tired or bloated afterwards, so it’s best to rest at home.
Step 3: Sperm collection or retrieval
Time: Same day as egg collection
Location: Clinic
On the day of egg collection, the sperm provider will give a fresh sample at the clinic — usually by ejaculation. If frozen sperm is being used, it will be thawed and prepared in the lab.
If sperm can’t be produced or released naturally, a surgical sperm retrieval may be done. This is typically a quick outpatient procedure under local anaesthetic, where sperm is collected directly from the testicles or epididymis using a fine needle.
Step 4: Fertilisation using ICSI
Time: Within hours of egg and sperm collection
Location: Lab
This is the key step that sets ICSI apart from standard IVF. A skilled embryologist will use a microscope and a fine glass needle to inject a single healthy sperm directly into each mature egg.
This process helps overcome barriers like poor sperm movement or shape, and increases the chance of fertilisation for each egg. The fertilised eggs are then placed in an incubator, where they are carefully monitored for signs of normal development.
Step 5: Embryo development and transfer
Time: 3–6 days after fertilisation
Location: Lab and clinic
As your embryos develop, they’ll be closely tracked by the embryology team. The goal is to reach the blastocyst stage (usually by day 5), which is when embryos are most likely to lead to a successful pregnancy.
When the timing is right, one embryo will be selected for transfer into the uterus — a quick and usually painless procedure done in the clinic. If you have other embryos that develop well, they can be frozen for future use. After transfer, you’ll be supported through the two-week wait before taking a pregnancy test.
How long does ICSI take?
Typical timeline: 4 to 6 weeks
ICSI is performed as part of an IVF cycle, so the full treatment typically takes 4 to 6 weeks from the start of ovarian stimulation to embryo transfer. You may also need additional time before this for initial consultations, testing, or sperm retrieval (if required).
If you have embryos frozen for future use, any later transfer cycles will be shorter, as no egg collection or ICSI will be needed again.
Understanding ICSI success rates
ICSI is very effective at helping an individual sperm fertilise an egg — but fertilisation is only one part of the bigger picture. Like IVF, success depends on several other factors, including the age and egg quality of the person undergoing treatment, the overall embryo quality, and any underlying fertility challenges.
Although ICSI helps bypass sperm-related issues, it doesn’t necessarily improve the overall chance of pregnancy compared to standard IVF. That’s why most clinics don’t publish separate success rates for ICSI cycles. In general, live birth rates for ICSI are similar to those for IVF — and age remains the most significant factor. [1]
Here’s what we do know:
- Around 60–70% of mature eggs injected using ICSI will fertilise — which is considered a good fertilisation rate. [5]
- The embryo transfer stage, implantation success, and live birth outcome still follow the same patterns as standard IVF, with age and uterine health playing a major role.
- If you’ve had previous IVF with poor or no fertilisation, ICSI can significantly improve the chance of reaching embryo transfer. [1,6]
While ICSI improves the odds of fertilisation for many, it doesn’t guarantee pregnancy — and isn’t routinely recommended if there are no issues with sperm. Your clinic will guide you on whether it’s the right approach for your situation, and explain how your personal chances of success stack up.
Is ICSI more successful than IVF?
Not necessarily — ICSI and IVF have very similar success rates when it comes to achieving a pregnancy and live birth. The key difference is that ICSI is designed to help when fertilisation might not happen through standard IVF, usually due to sperm-related issues.
ICSI is highly effective at improving fertilisation rates in these cases, but it doesn’t increase the chance of pregnancy if sperm quality isn’t a known issue. That’s why clinical guidelines don’t recommend using ICSI routinely for unexplained infertility or when standard IVF is likely to work just as well.
According to HFEA data, the live birth rate for IVF-only cycles is around 25.8%, whereas the live birth rate for ICSI cycles of IVF is approximately 31% — so it’s a little higher. [2]
While ICSI can be the better choice for certain people, it’s not universally “more successful” — and isn’t always needed. Your doctor will recommend the right approach based on your fertility history, test results and any past treatment outcomes.
What happens after ICSI?
Once ICSI is complete — meaning a single sperm has been injected into each mature egg — the fertilised eggs are placed in an incubator and monitored closely over the next few days to see which ones develop into embryos. You’ll usually get updates from your clinic during this time.
If embryos develop as expected, one (or occasionally two) will be selected for embryo transfer, which takes place 3 to 6 days after egg collection. This is a simple, usually painless procedure done at the clinic, where the embryo is placed into the uterus using a thin catheter. [1,7,8]
After transfer, you’ll enter the two-week wait before taking a pregnancy test — often one of the most emotionally intense parts of treatment. Your clinic may recommend taking progesterone to support the uterine lining during this time. If there are good quality embryos left over, they can be frozen for future use.
What are the risks of ICSI?
Like any fertility treatment, ICSI comes with some potential risks — both from the procedure itself and the underlying reasons it’s being used. While many people go through ICSI without complications, it’s important to be aware of the possible outcomes so you can make informed decisions and ask the right questions.
- Slightly increased risk of egg damage: Because the sperm is injected directly into the egg, there’s a small chance the egg may be damaged in the process and won’t survive. [1]
- Not all eggs will fertilise: On average, around 60–70% of injected eggs fertilise — so some may not develop further. [5]
- Potentially higher risk of passing on male infertility: If infertility is linked to a genetic condition (especially involving the Y chromosome), it could be passed on to any sons conceived through ICSI. [9]
- Genetic or chromosomal conditions in rare cases: If sperm issues are linked to conditions like cystic fibrosis or chromosomal abnormalities, genetic counselling and testing may be recommended before treatment. [1]
Your clinic should talk you through these risks in more detail, and support you in deciding whether ICSI is the right option for you or your family.
Is ICSI available on the NHS?
Yes, ICSI is available on the NHS — but eligibility varies depending on where you live and whether you meet certain criteria. Because ICSI is more specialised than standard IVF, it’s usually only offered when there’s a clear medical reason, such as a diagnosed sperm-related fertility issue.
In most cases, NHS funding for ICSI is considered when:
- You or your partner have been trying to conceive for a set amount of time (usually 1–2 years depending on your age and local policy)
- There is medical evidence of male-factor infertility (like very low sperm count or sperm retrieved surgically)
- Other eligibility criteria are met — including age, BMI, previous children, and sometimes smoking status
The rules are set by your local Integrated Care Board (ICB), and they can differ across the UK. You can speak to your GP or fertility specialist about a referral and check what’s available in your area.
Use our NHS eligibility tool to find out what support you might be able to access.
Your NHS Eligibility
Use our NHS IVF Eligibility Calculator to discover if you can access free ICSI.
How much does ICSI cost?
If you’re having ICSI privately, costs can vary depending on the clinic and what’s included in your treatment package. On average in the UK, ICSI adds around £780–£1,675 (an average of £1,375) to the base cost of an IVF cycle.
That means a full IVF with ICSI cycle can typically range from £3,530 to £14,175 (an average of £8,920), though some clinics may price it higher — especially if medications, consultations, blood tests, and embryo freezing are billed separately.
Because ICSI is an add-on used for specific cases, it’s important to ask your clinic for a detailed breakdown of what’s included in your quote — and whether the use of ICSI is medically recommended in your situation.
Where can I find an ICSI clinic?
You can use our Find a Clinic page to explore UK fertility clinics that offer ICSI, compare success rates, and read honest reviews from people in our community. Whether you’re just starting out or ready to book a consultation, our filters help you find clinics based on location, price range, specialisms, and treatment types — including ICSI.
If you’re not sure where to start, our Clinic Matching Tool can guide you through your options based on your medical history, preferences and priorities. It’s completely free to use and designed to take the stress out of searching — helping you feel informed, confident, and in control of your next step.
Already have a Fertility Mapper account? Log in here to pick up where you left off and find your ICSI clinic.
I’ve had ICSI and it didn’t work – what next?
You’re not alone — it’s incredibly hard when treatment doesn’t lead to a pregnancy, especially after everything you’ve invested physically and emotionally. Many people need more than one cycle to have success, and it’s completely valid to take time to rest, recover, and reflect before deciding what’s next.
Your clinic may suggest waiting a couple of months before trying again, to allow your body to recover and your hormone levels to reset. When you’re ready, you can talk through your treatment outcome in detail with your doctor — they may adjust your protocol, explore further testing, or recommend other options like using donor sperm or embryo.
How does ICSI compare to other treatments?
Treatment
Who
Hormones
Timeline
Average cycle cost
IVF
People treating infertility
Medication for 2-4 weeks
6-9 weeks
£7,545
ICSI
People with sperm-related infertility needing lab-assisted fertilisation
Medication for 2–4 weeks
6–9 weeks
£8,920
IUI
People who can’t use sex to conceive, or before trying IVF
None, or minimal
4 weeks
£1,900
Donor egg IVF
People who can’t use their own eggs in IVF
Minimal
4 weeks
£10,374
Egg freezing
People preserving their fertility
Medication for 2-4 weeks
4-6 weeks
£6,497
Surrogacy
Same sex male couples or people who can’t carry a pregnancy
None
4 weeks
£20-30,000
Cycle monitoring
Heterosexual couples using sex to conceive
None
4 weeks
£500
Find the right ICSI clinic for you
Choosing a fertility clinic is a big decision — and we’ve made it clearer.
Summary
treatment that can offer clarity and hope in complex fertility paths — especially when sperm-related challenges are part of the picture. While it’s not a guaranteed solution, and won’t be right for everyone, it remains one of the most effective options for improving fertilisation when the sperm needs extra help reaching the egg.
As always, the best next step is a conversation with a fertility specialist who can walk you through whether ICSI makes sense for your situation — and what to expect. And if you’re looking for more guidance, real reviews, or support along the way, we’re here to help you make informed, confident choices.
ICSI FAQs
How is ICSI different from IVF?
The main difference lies in how fertilisation happens in the lab. With IVF, eggs and sperm are mixed together and left to fertilise naturally — relying on the sperm’s ability to reach and penetrate the egg. With ICSI (Intracytoplasmic Sperm Injection), a single sperm is selected and injected directly into the centre of each mature egg by an embryologist.
ICSI is often used when there are sperm-related issues — such as low count, poor motility, or previous failed IVF fertilisation. It tends to have a higher fertilisation rate than IVF (around 73% vs 65%) but also results in more eggs going unused, often due to immaturity or being unsuitable for injection. While ICSI may produce more embryos per egg used, overall success rates (in terms of pregnancy and live birth) are similar when sperm quality isn’t a concern. [3]
That’s why ICSI isn’t recommended for everyone. It’s best reserved for when there’s a clear reason to use it — not just as a default. Your clinic will help decide whether IVF or ICSI is more appropriate based on your individual fertility factors, especially the sperm characteristics.
Is ICSI painful?
No, ICSI itself isn’t painful — because it all happens in the lab. The injection of a single sperm into each egg is done by an embryologist using specialised equipment, and you won’t feel this part at all.
What you might feel are some of the steps that come before or after, as part of the broader IVF process. These can include:
- Hormone injections, which some people find a bit uncomfortable but are usually manageable with the right technique and support.
- Egg collection, which is a short procedure done under sedation or anaesthetic — so you won’t feel pain during it, but you might feel sore or bloated afterwards.
- Sperm retrieval, which is painless if given by ejaculation, but may involve a minor surgical procedure (under local anaesthetic) if sperm is being retrieved directly from the testicles.
Are ICSI babies normal?
Most children born through ICSI (Intracytoplasmic Sperm Injection) are healthy and develop typically — just like children conceived without fertility treatment. That said, ICSI is a relatively new technology, and researchers continue to study long-term outcomes to fully understand any additional risks.
Current evidence shows that there may be a slightly higher risk of certain health conditions in babies born through ICSI compared to naturally conceived children — such as congenital genitourinary conditions (like hypospadias in boys), imprinting disorders, or developmental concerns. But these risks are still small, and it’s unclear whether they’re caused by the ICSI procedure itself or the underlying reasons the treatment was needed in the first place (like severe male-factor infertility, which may have a genetic basis). [4,10]
What’s important to know is this: the vast majority of ICSI-conceived babies are born healthy, and many go on to thrive just like their peers. If you’re considering ICSI, your clinic should talk you through any potential risks — especially if there are known genetic factors — and may offer genetic counselling if needed. As with all fertility treatments, informed and supported decision-making is key.
Are girls more common with ICSI?
ICSI is associated with a slightly higher chance of having a female baby. While IVF typically results in around 53.7% male births, this figure drops to 50.1% with ICSI. In other words, ICSI appears to slightly reduce the odds of a male live birth, gently tipping the balance towards girls. This isn’t a guarantee — but it is a notable statistical trend observed across large-scale studies, including over 9,000 deliveries following frozen embryo transfer. [11]
Researchers believe this shift may be due to how sperm are selected during ICSI. Unlike IVF, where sperm naturally compete to fertilise the egg, ICSI involves choosing a single sperm to inject directly into the egg. It’s thought that Y-bearing sperm (which produce male embryos) may be less likely to meet the selection criteria — particularly when judged on shape and movement — meaning X-bearing sperm (which lead to female embryos) may be used more often.
It’s also possible that ICSI bypasses some of the biological advantages Y-bearing sperm might have in natural fertilisation, slightly altering the natural male-to-female ratio. Whatever the mechanism, the data is clear: ICSI tends to result in more female births compared to IVF.
Can you pick gender with ICSI?
No, you can’t choose your baby’s gender with ICSI unless it’s part of a medically approved process. That said, ICSI has been shown to slightly increase the likelihood of female births — though not enough to be used for gender selection. [11]
Does ICSI lead to twins?
ICSI itself doesn’t directly increase the likelihood of twins — but twins can still happen, especially if more than one embryo is transferred. When only one embryo is transferred, there’s still a small chance of identical (monozygotic) twins, which can happen naturally in any pregnancy. In IVF, including ICSI cycles, this happens slightly more often than in natural conception.
In a 2021 study, monozygotic twinning occurred in about 1.2% of single embryo transfers. The biggest factor linked to this was assisted hatching — a lab technique sometimes used alongside ICSI — which was associated with more than double the risk of identical twins. So while ICSI alone isn’t a major driver of twins, certain related techniques may play a role. [12]
Do you get more embryos with ICSI?
ICSI can improve the chances of fertilisation when sperm quality is a concern, but it doesn’t always result in a higher number of healthy embryos. In fact, some research has found that embryos created through ICSI may be more likely to have chromosomal abnormalities compared to those created through standard IVF. This may be linked to how the egg is handled during the procedure. [13]
So while ICSI can be a helpful option in specific cases, especially where sperm can’t fertilise the egg without assistance, it doesn’t reliably produce more embryos overall — and may come with trade-offs in embryo quality. [1]
Does ICSI pick the best sperm?
Not exactly. ICSI doesn’t guarantee the “best” sperm is used — it simply allows an embryologist to choose a single sperm to inject directly into the egg, bypassing the natural selection that usually happens in the body or in traditional IVF. [1]
Sperm are typically selected based on how they look and move under a microscope, but this doesn’t always reflect what’s happening at the genetic or chromosomal level. There are several lab techniques that can improve sperm selection — like swim-up, density gradient, or more advanced methods like IMSI or microfluidics — but even with these, there’s no gold-standard way to reliably identify the most genetically competent sperm. [14]
Sources
1. https://www.hfea.gov.uk/treatments/explore-all-treatments/intracytoplasmic-sperm-injection-icsi/
2. https://app.powerbi.com/view?r=eyJrIjoiYzkwYjVmNmQtZjNkNC00ODM0LWE4NmItMDgyMzE0NzhmYzE0IiwidCI6IjU3ODA1YjhkLTc5MzctNGMyYi1hZjMyLWQxNmE0NzNhZWMyYyIsImMiOjh9
3. https://pmc.ncbi.nlm.nih.gov/articles/PMC8812449/
4. https://academic.oup.com/ije/article-abstract/34/3/696/682233?redirectedFrom=fulltext
5. https://www.uhcw.nhs.uk/ivf/treatments/icsi/
6. https://pmc.ncbi.nlm.nih.gov/articles/PMC10362230/
7. https://www.guysandstthomas.nhs.uk/health-information/ivf-treatment/step-4-fertilisation
8. https://pmc.ncbi.nlm.nih.gov/articles/PMC4046257/
9. https://pmc.ncbi.nlm.nih.gov/articles/PMC3600334/
10. https://pmc.ncbi.nlm.nih.gov/articles/PMC2424218/
11. https://pmc.ncbi.nlm.nih.gov/articles/PMC10548202/
12. https://pubmed.ncbi.nlm.nih.gov/33258063/
13. https://pmc.ncbi.nlm.nih.gov/articles/PMC7331232/
14. https://pmc.ncbi.nlm.nih.gov/articles/PMC8700516/