Intracytoplasmic Sperm Injection (ICSI)

What is ICSI?

Intracytoplasmic sperm injection (ICSI) is a specialized assisted reproduction procedure to aid in egg fertilization during in vitro fertilization (IVF). Normally, a sperm attaches to the egg’s outer layer, called the zona pellucida (similar to a bird egg’s shell), and penetrates it to reach the inner part of the egg, known as the cytoplasm, where fertilization occurs. However, when there are issues with sperm quality or if the egg’s outer layer is tough to penetrate, ICSI may be indicated.

This technique involves directly injecting a single sperm into the egg, thus eliminating potential barriers to egg fertilization. ICSI adds a step to the traditional IVF process: ovarian stimulation, egg and sperm retrieval, fertilization (using ICSI instead of allowing sperm to fertilize the egg on its own in a lab dish) and embryo transfer.

IVF alone has limitations in treating male infertility, as it relies on the natural ability of sperm to fertilize an egg. However, ICSI emerged in the 1990s as a solution to overcome these limitations, and the results have been favorable. ICSI has become a standard approach to help with fertilization when sperm quality is low, and to help patients who have a history of poor fertilization in apparently-normal sperm. Male factor infertility is a significant contributor to infertility causes, accounting for about half of all cases, either as the sole cause or in combination with other causes of a couple’s infertility.

Who can benefit from intracytoplamic sperm injection?

There are certain criteria to consider when deciding if ICSI is the right treatment option. This procedure is typically recommended for couples who have had unsuccessful conventional IVF treatments or for those with severe male factor infertility. ICSI can also be beneficial for couples with unexplained infertility or when anatomical anomalies make it difficult for sperm to fertilize an egg.

Overall, ICSI offers a more targeted approach to overcome specific sperm-related issues. As with any medical procedure, it is important to consult with a specialist to determine if ICSI or another fertility treatment is the right option for each individual case.

Situations that may warrant ICSI treatment

ICSI is used for female and male infertility conditions, such as:

• Previous failed or low fertilization with IVF.
• Low sperm production.
• Irregular sperm shape or movement.
• Sperm that have trouble attaching to the egg.
• Few eggs retrieved during IVF.
• Eggs with a thick zona pellucida.
• Unexplained infertility.
• Obstructed male reproductive tract conditions that inhibit sperm transport during ejaculation.

Occasionally, even with normal sperm parameters, a fertility doctor may recommend ICSI due to previous fertilization failure or when the sperm is used to inject previously frozen eggs, as it has been shown to be beneficial in these special cases.

What to expect during the ICSI procedure

The ICSI process involves several key steps to ensure the successful fertilization of an egg, starting with the collection of sperm from the male partner or a sperm donor. It occurs at the point in IVF after eggs have been retrieved for fertilization.

The semen, most often collected via masturbation, is washed to remove debris and immobile sperm. It is important to note that previous semen analyses are performed to assess the quality of the sample and determine the most suitable fertilization method prior to any proposed IVF cycle. Good quality semen will have optimal number of sperm that have normal shape and progressive motility needed for fertilization.

The mature eggs retrieved in IVF are then fertilized with a single healthy sperm through direct injection into the egg’s cytoplasm, bypassing the normal entry of sperm in the IVF fertilization process.

This direct injection method increases the chances of successful fertilization for these patients. In contrast, in a typical IVF procedure millions of sperm are prepared and added to a laboratory dish (containing the retrieved eggs) to facilitate fertilization, as would happen in natural fertilization when the sperm encounters the female egg in the fallopian tube.

The remaining steps of the IVF process are resumed, with  embryos being cultured in the lab for commonly five to six days until they form blastocysts (high grade embryos). These embryos can be biopsied to ensure they exhibit a normal chromosome makeup (aka “euploid blastocyst”) and can be cryopreserved for current or future pregnancy attempts. The embryos are subsequently transferred to the woman’s uterus for implantation and growth, aiming for a successful full-term pregnancy. Once fertilization occurs, the chance of giving birth is the same as with traditional IVF treatment.

While the entire IVF procedure takes around 2-3 weeks, the process of injecting the sperm into the eggs takes place after the egg retrieval and is completed within a short time frame relative to the entire cycle. It is accomplished by an embryologist utilizing a specialized microscope and equipment. Using a thin pipette, the lab specialist draws in a viable sperm demonstrating good movement, punctures the egg’s zona pellucida and injects the single sperm.

Success rates and potential risks of ICSI

This technique has shown promising results in improving fertilization rates and achieving successful pregnancies, especially in cases of poor sperm quality. ICSI helps reach the fertilization goal of 50%-80%, according to the American Society for Reproductive Medicine (ASRM).

However, the process of fertilization doesn’t ensure healthy embryos or successful pregnancies, and that is relative to cases completed with and without ICSI. Optimal conditions for both eggs and sperm including genetic integrity are crucial for successful implantation of an embryo and ongoing pregnancy development to term.

Like any medical procedure, ICSI carries potential risks. One risk is egg damage during the procedure, although the extent of this risk is minimized through experience and specialized training. Studies suggest a slightly elevated chance of birth defects with ICSI compared with standard IVF, but it’s unclear whether this is due to the technology or the patients’ underlying fertility causes.

Certain conditions, like abnormalities in sex chromosomes or Angelman syndrome, are linked to ICSI but are rare (less than 1% of ICSI births). Despite this, the overall risk remains low and comparable to spontaneous conception rates (1.5%-3% birth defect rate).

In many cases, the benefits of using ICSI in IVF outweigh the risks, as not using ICSI can lead to low fertilization rates or failed fertilization. However, individual success rates and risks can vary by case and clinic. It’s crucial to research thoroughly and consult with a medical professional before undergoing ICSI treatment.