ICSI (Intracytoplasmic Sperm Injection): How It Works, Who Needs It, and What to Expect

In short: ICSI is the injection of a single sperm directly into the egg in the IVF laboratory. It is used mainly when sperm count, movement or shape is poor, when fertilisation failed in earlier attempts, or when sperm is retrieved from the testicle.

If you and your partner have been told that IVF alone may not be enough to achieve fertilization, Intracytoplasmic Sperm Injection (ICSI) may offer a way forward. ICSI is a well-established laboratory technique used alongside IVF, in which a single, carefully selected sperm is injected directly into an egg to help fertilization take place. It is often recommended when sperm numbers are low or when previous IVF cycles did not result in fertilization, because it does not rely on sperm reaching and penetrating the egg on their own.

During the procedure, our embryology team uses an inverted microscope and fine micromanipulation tools to gently guide a single sperm through the egg’s outer membrane and into its inner fluid, the cytoplasm. In many IVF laboratories, a large proportion of injected eggs go on to fertilize successfully, though every couple’s biology is different and no clinic can guarantee an individual outcome. Your fertility specialist can walk you through what to realistically expect based on your own test results.

What is the difference between ICSI and IVF?

ICSI and IVF are not two different treatments. They are two ways of fertilising the egg within the same programme. The only difference is one step in the laboratory: how the sperm gets into the egg. Every other step is exactly the same.

In IVF (conventional fertilisation)

Each egg is placed in a dish with a large number of prepared sperm, and a sperm is left to enter the egg by itself, as happens in natural conception but in the laboratory.

In ICSI

The embryologist chooses a single sperm and injects it directly into each mature egg with a very fine needle under the microscope.

What stays the same in both

·       Stimulation of the ovaries with injections, followed by ultrasound.

·       Egg retrieval under light sedation.

·       Preparation of the sperm sample.

·       Growing the embryos in the laboratory, then transferring them to the uterus or freezing them.

·       What the patient feels, the number of visits and the date of the pregnancy test.

At a glance

	IVF (conventional fertilisation)	ICSI
How the egg is fertilised	The egg is placed with thousands of sperm in a dish	One sperm is injected into the egg
Sperm needed	A large number with good movement	One healthy sperm per egg is enough
When it is used	When the semen analysis is normal	When sperm is poor, or fertilisation failed before
The other steps	The same	The same

When is ICSI chosen?

·       A low sperm count, poor movement or abnormal shape.

·       Sperm retrieved surgically from the testicle or epididymis.

·       Failed or poor fertilisation in an earlier IVF attempt.

·       Use of frozen eggs or frozen sperm, or when the embryos are to be genetically tested.

·       A small number of eggs collected.

Which is better?

Neither is better for everyone. When the sperm is normal, pregnancy rates are similar with both, and ICSI does not by itself raise the chance of pregnancy. When the sperm is poor, ICSI is the right choice because it overcomes that problem. Dr. Layyous chooses the method for each couple after studying the semen analysis and the results of any earlier attempts.

For all the steps of the programme, read our guide to [IVF: steps and success rates](/ivf-steps-and-success-rates/).

When Might ICSI Be Recommended?

Your doctor may suggest ICSI in a number of situations, including:

• Male infertility factors such as low sperm count, poor sperm motility, abnormal sperm shape, or difficulty penetrating an egg naturally — including cases of azoospermia (no sperm in the ejaculate).
• A previous IVF cycle where fertilization did not occur or was unexpectedly low.
• A male partner who has had a vasectomy, where sperm are retrieved directly from the testicles or epididymis.
• Difficulties with erection or ejaculation that make natural sperm collection challenging.
• Couples who have only a small number of eggs retrieved may ask about ICSI; however, when the sperm are normal, studies show that ICSI does not increase the chance of a baby compared with standard IVF, so the choice is individualised.

How conventional insemination in the laboratory fits into a treatment cycle is described in our guide to the steps of IVF.

Note: recommendations vary between clinics — some reserve ICSI for significant male-factor infertility, while others offer it more broadly. Your fertility specialist will discuss which approach fits your situation.

Watch IVF and ICSI procedure videos

The ICSI Procedure, Step by Step

• The ovaries are stimulated with medication to encourage the development of multiple eggs.
• Eggs are collected using a fine, hollow needle guided by ultrasound — a short, monitored procedure.
• In the lab, an embryologist picks up a single sperm using a very delicate needle, gently passes it through the egg’s outer shell, and injects it into the cytoplasm. This gives the egg the opportunity to fertilize, though it cannot guarantee that fertilization will occur.
• Fertilized eggs are cultured and monitored, and embryos are typically transferred to the uterus either 2–3 days after fertilization or at day 5, once they reach the blastocyst stage.
• A pregnancy test is usually recommended about two weeks after the embryo transfer.

Inside the ICSI Laboratory: Photos

How Sperm Are Retrieved for ICSI

• If sperm are present in the semen, a sample can usually be collected by normal ejaculation on the same day as egg collection.
• If no sperm are present in the semen, your doctor can retrieve sperm directly from the male partner under local or general anesthesia using one of the methods below.

Percutaneous Epididymal Sperm Aspiration or Extraction (PESA, MESA)

These techniques are generally used when the male partner has one of the following:

• Absence of the vas deferens (the tube that normally carries sperm from the epididymis into the seminal fluid).
• A past infection that has caused a blockage.
• A previous vasectomy where surgical reversal was unsuccessful.

Testicular Sperm Aspiration or Extraction (TESA, TESE)

In this approach, sperm are obtained directly from the testicular tissue itself — either by fine-needle aspiration or by taking a very small tissue sample surgically. The retrieved sperm are then used for the ICSI procedure described above.

TESA/TESE may be recommended in the following situations:

• No sperm are found in the epididymis.
• The epididymis is absent or blocked.
• Sperm retrieval is planned ahead of the treatment cycle, with the collected sperm frozen for later use.

Learn more about our IVF, ICSI, TESA/TESE and IUI outcomes

Things to Keep in Mind

• As with standard IVF, pregnancies achieved through ICSI carry the same general risk of multiple pregnancy and, rarely, ectopic pregnancy. Your doctor will discuss these considerations with you before starting treatment.

Men with very low sperm counts or no sperm should have genetic tests (karyotype and Y-chromosome microdeletions, and cystic fibrosis gene testing if the vas deferens is absent) before ICSI, because some of these causes can be passed on to a son. Children born after ICSI are healthy in the great majority of cases, although a slightly higher rate of some birth defects has been reported, partly linked to the underlying male infertility.

If you would like to discuss whether ICSI is a suitable option for you and your partner, our fertility team at Dr. Najeeb Layyous Clinic is happy to review your history and guide you through the next steps in a supportive, unhurried consultation.

Dr Najeeb Layyous F.R.C.O.G

Consultant Obstetrician, Gynecologist and Infertility Specialist