ICSI, or intracytoplasmic sperm injection, is the procedure in which a single selected sperm cell is injected directly into a mature egg in the embryology laboratory. It is performed during the fertilization stage of in vitro fertilization (IVF) treatment; it is not a separate treatment on its own.
It is most commonly considered in cases where there are significant abnormalities in sperm parameters or when fertilization could not be achieved in a previous treatment cycle. The decision regarding suitability is made individually by the IVF specialist after evaluating the couple as a whole, taking laboratory findings into consideration.
For couples researching IVF treatment or the ICSI procedure in İzmir, the decision to perform ICSI is based on a comprehensive assessment of sperm characteristics, the number of retrieved eggs, previous treatment outcomes, and the couple's overall health status.
ICSI is the abbreviation for the English term "intracytoplasmic sperm injection." It refers to the injection of a single selected sperm cell directly into the cytoplasm of a mature egg using an extremely fine glass needle. The World Health Organization (WHO) infertility guideline also describes the technique, first introduced in 1992, as a fertilization method based on the injection of a single sperm directly into an oocyte.
During IVF treatment, ICSI is performed entirely in the embryology laboratory under a microscope. In other words, it is not a procedure carried out inside the patient's body.
ICSI does not represent the entire IVF process. Ovarian stimulation, egg retrieval, and embryo transfer are separate stages of treatment. ICSI is only one step that determines how fertilization will be achieved.
Conventional IVF and ICSI differ in the way fertilization occurs. In conventional IVF, sperm and eggs are placed together in the laboratory, allowing fertilization to occur naturally.
| Comparison | Conventional IVF | ICSI |
|---|---|---|
| Fertilization method | Prepared sperm are placed together with the eggs, and fertilization occurs without injection | A single sperm is injected directly into the egg |
| Sperm selection | Fertilization largely depends on the sperm's natural ability to reach and penetrate the egg | The embryologist selects a single suitable and motile (or viability-confirmed) sperm |
| Typical indication | Cases with appropriate sperm characteristics | Particularly cases involving certain male-factor infertility or fertilization problems |
The original and most established indication for ICSI is male-factor infertility. As stated in the 2026 opinion document of the American Society for Reproductive Medicine (ASRM), the technique was developed in 1992 to improve fertilization in couples experiencing fertilization failure due to male-factor infertility. Over the years, its use has expanded considerably.
However, this increased use does not mean that ICSI should be routinely performed for every patient undergoing IVF. Below are situations in which ICSI may be considered.
Conditions in which sperm characteristics make fertilization more difficult represent the classic indication for ICSI. A low sperm count and significant impairment in sperm motility are among the most common male-factor conditions for which the technique is considered.
In severe male-factor infertility, the likelihood of a sperm fertilizing an egg naturally is reduced. Therefore, injecting a single sperm directly into the egg may be a reasonable approach.
Sperm morphology, or the shape of the sperm, should always be interpreted together with the other semen parameters. Poor morphology alone, when sperm count and motility are normal, does not necessarily require ICSI. The same ASRM opinion document reports that, in such cases, ICSI did not demonstrate a clear advantage over conventional IVF. As always, the decision should be based on the couple's overall clinical picture rather than a single laboratory finding.
In certain cases where no sperm are present in the semen, sperm can be obtained surgically from the testicle or the sperm ducts. According to the 2026 guideline of the European Association of Urology (EAU), sperm retrieval procedures from the epididymis or testis (such as MESA, PESA, TESA, and TESE) may be used in combination with ICSI to achieve pregnancy in conditions such as obstructive azoospermia.
The number of sperm obtained through these procedures is often limited. When only a few sperm cells are available, ICSI becomes an appropriate method because it allows fertilization to be performed individually for each egg.
For this group of patients, genetic evaluation is a separate and important consideration. The same guideline emphasizes that couples should receive genetic counseling before treatment if the male partner has a karyotype (chromosomal) abnormality. For example, certain deletions on the Y chromosome may be passed on to male offspring, and this possibility should be discussed before treatment.
Complete fertilization failure or lower-than-expected fertilization rates in a previous conventional IVF cycle is one of the situations in which ICSI may be considered for a subsequent treatment cycle. The same ASRM opinion document states that ICSI can improve fertilization rates when conventional IVF has previously resulted in complete or unexpectedly poor fertilization. The aim is to reduce the likelihood of the same problem recurring. Therefore, previous treatment outcomes play an important role in planning a new cycle.
ICSI may also be considered when only a very limited number of usable sperm are available. In samples obtained surgically or in frozen-thawed specimens with only a small number of remaining sperm cells, the ability to individually select one sperm for each egg offers a practical advantage. However, the fact that sperm has been frozen does not automatically mean that ICSI is required.
ICSI is not a procedure that should be routinely performed for every patient. The decision is based on a comprehensive evaluation of the couple rather than a single finding, and treatment is individualized. This planning generally involves four key decisions: the ovarian stimulation protocol to be used, whether fertilization will be achieved through conventional IVF or ICSI, the day of embryo transfer, and the number of embryos to be transferred.
ICSI is carried out through the following steps:
After egg retrieval, the surrounding support cells are carefully removed in the laboratory so that the maturity and condition of each egg can be clearly evaluated. Current recommendations specify that ICSI should only be performed on mature eggs and that every effort should be made to avoid damage to the egg throughout the procedure. The maturity status of each egg is documented.
The sperm sample is prepared in the laboratory, and the most suitable sperm cell for injection is selected. The goal is to identify the single sperm that is most appropriate for fertilization.
The actual microinjection procedure is performed under a microscope. The egg is gently held in place with a specialized holding pipette, and the selected sperm cell is injected into the inner part of the egg (the cytoplasm) using an extremely fine glass needle. This procedure is repeated individually for every mature egg obtained.
For patient safety, the identities of both the egg and sperm samples are verified before fertilization through either a double-check by a second professional or an electronic witnessing system. This step is a standard quality assurance measure.
Following the injection, the laboratory evaluates whether fertilization has occurred. This assessment is usually performed approximately 16–17 hours after the procedure. As the fertilized eggs begin developing into embryos, their progress is carefully monitored in the laboratory. If an embryo develops appropriately, either embryo transfer during the same treatment cycle or embryo cryopreservation (freezing) may be considered.
In some treatment cycles, however, no embryo may develop sufficiently to be suitable for transfer or freezing. Each of these outcomes is discussed with you throughout the treatment process.
There is no definitive answer to the question, “Does ICSI work?”
Although the most common question during treatment is whether fertilization has occurred, the ultimate goal is the birth of a healthy baby. Therefore, an approach that increases the fertilization rate does not automatically result in more babies being born.
The outcome depends on the combined effect of many different factors rather than a single variable. These include the woman's age, the number and maturity of the retrieved eggs, egg quality, sperm characteristics, the underlying cause of infertility, previous treatment outcomes, embryo development, uterine and endometrial characteristics, the quality of the embryology laboratory, and an individualized treatment plan. The importance of each of these factors varies from one couple to another, which is why no single success rate applies to everyone.
The first step after ICSI is the assessment of fertilization. The development of fertilized eggs into embryos is monitored in the laboratory, and the embryos are evaluated according to their developmental progress. Based on this evaluation, a decision is made as to whether the embryo will be transferred during the same treatment cycle or frozen for future use.
Following embryo transfer, the pregnancy testing process begins. The timing of the pregnancy test depends on the day of embryo transfer and the individualized treatment plan. All of these steps are planned together with you as part of the overall IVF treatment process.
Although the information above explains what ICSI is and how it is performed, determining whether the procedure is appropriate for you requires an individual medical evaluation. When making this decision, sperm characteristics, the number of eggs, previous treatment outcomes, and the couple's medical history are assessed together. Information found online provides only a general overview. The choice of treatment should be made following consultation with a physician specializing in reproductive medicine.
During the infertility journey, receiving guidance from a specialist with whom you can openly discuss your questions and evaluate your options together can be valuable. If you would like to learn more about ICSI and IVF treatment in İzmir or have your previous treatment results evaluated, you can schedule a consultation appointment with Assoc. Prof. Dr. Funda Göde.
Kaynakça
American Society for Reproductive Medicine ve Society for Assisted Reproductive Technology Uygulama Komiteleri. Intracytoplasmic sperm injection for nonmale factor indications: a committee opinion. Fertility and Sterility, 2026 (erken görünüm / baskıda). doi:10.1016/j.fertnstert.2026.03.032
ESHRE Good Practice in the IVF Laboratory Working Group. ESHRE recommendations on Good Practice in the IVF laboratory. Human Reproduction, 2026. doi:10.1093/humrep/deag096
European Association of Urology (EAU). EAU Guidelines on Sexual and Reproductive Health. Limited Update, Mart 2026.
Dünya Sağlık Örgütü (WHO). Guideline for the prevention, diagnosis and treatment of infertility. Cenevre: WHO. ISBN 978-92-4-011577-4.
No, there is no certainty or guarantee. Whether fertilization occurs depends on egg maturity, sperm characteristics, and biological factors. ICSI can increase the likelihood of fertilization, but it does not guarantee the same outcome for every egg.
A single sperm cell is used for each mature egg. However, the treatment plan is determined based on the number of mature eggs retrieved and the number of suitable sperm. In other words, the answer to the question “Is a single sperm enough?” depends on how many eggs will be inseminated.
The microinjection itself is performed on the egg in the laboratory. The patient does not directly feel this procedure. The parts of the process that may be associated with pain or discomfort—such as egg retrieval—are other stages and are evaluated separately.
The duration of the ICSI procedure in the laboratory varies depending on the number of mature eggs and the laboratory’s workflow. Microinjection is performed in the laboratory on the day of egg retrieval. Fertilization is typically checked 16–17 hours later. The entire treatment, however, is a separate process spanning several weeks, from ovarian stimulation to embryo transfer.
The main factor determining the likelihood of a twin pregnancy is not the use of intracytoplasmic sperm injection (ICSI). This likelihood depends more on factors such as the number of embryos transferred and embryo division. The number of embryos to be transferred is a decision made on a case-by-case basis.
Note: This content is for general informational purposes only and does not replace diagnosis or treatment. A physician evaluation is required for personal diagnosis and treatment planning.
