What Is ICSI? Who Needs ICSI?

In an IVF (in vitro fertilization) cycle, the most critical step is achieving successful fertilization between sperm and egg.

Under normal circumstances, tens of thousands to hundreds of thousands of sperm are placed around the egg, allowing one sperm to naturally penetrate the outer layer of the egg and achieve fertilization. This is called conventional IVF.

However, in some cases, sperm are unable to successfully enter the egg. In such situations, a more advanced technique is required —

Intracytoplasmic Sperm Injection (ICSI).

ICSI is a laboratory technique in which an embryologist selects a single high-quality sperm under a high-powered microscope and injects it directly into the cytoplasm of the egg using an extremely fine glass needle to achieve fertilization.

The development of this technology has made pregnancy possible for many individuals who previously had little chance of conceiving naturally.

According to recommendations from the American Society for Reproductive Medicine (ASRM), common indications for ICSI include the following:

1. Male Factor Infertility

When sperm count is too low, motility is poor, or morphology is abnormal, sperm may have difficulty penetrating the egg naturally. Even with IVF, fertilization rates may remain very low.

Common conditions include:

· Poor sperm motility

· Abnormal sperm morphology

· Oligospermia or azoospermia requiring surgical sperm retrieval (testicular or epididymal sperm extraction)

· Impaired sperm–egg penetration ability (including genetic causes)

In these situations, ICSI can directly bypass fertilization barriers and significantly improve the chance of fertilization.

2. Poor Fertilization in Previous IVF Cycles

Even when semen analysis results are normal, prior IVF cycles may show:

· Total fertilization failure

· Low fertilization rate (typically <60%)

· Repeated embryo culture failure

There may be a “hidden fertilization defect,” such as abnormalities in sperm–egg recognition mechanisms or inadequate zona pellucida penetration.

In these cases, switching to ICSI is recommended to avoid repeated fertilization failure.

3. Special Oocyte Conditions

In certain egg conditions, natural fertilization is more difficult:

· Frozen–thawed oocytes

· In vitro matured (IVM) oocytes

· Limited number of eggs

· Advanced maternal age eggs

In these situations, ICSI is often recommended to avoid wasting precious oocytes.

4. Unexplained Infertility

Some couples have normal test results but are unable to conceive after a prolonged period. This is known as unexplained infertility.

These cases may involve abnormal sperm–egg interaction.
ICSI can directly overcome fertilization barriers and improve success rates.

References

1. Palermo, G., Joris, H., Devroey, P., & Van Steirteghem, A. (1992).
Pregnancies after intracytoplasmic injection of single spermatozoon into an oocyte. The Lancet, 340(8810), 17–18. https://doi.org/10.1016/0140-6736(92)92425-F

2. Practice Committee of the American Society for Reproductive Medicine. (2020).
Intracytoplasmic sperm injection (ICSI) for non-male factor indications: A committee opinion. Fertility and Sterility, 114(2), 239–245. https://doi.org/10.1016/j.fertnstert.2020.05.032

3. Practice Committee of the American Society for Reproductive Medicine. (2014).
The role of assisted hatching and micromanipulation in assisted reproductive technology: A guideline. Fertility and Sterility, 102(2), 348–351. https://doi.org/10.1016/j.fertnstert.2014.06.035

4. Zegers-Hochschild, F., Adamson, G. D., Dyer, S., Racowsky, C., de Mouzon, J., Sokol, R., Rienzi, L., Sunde, A., Schmidt, L., Cooke, I. D., Simpson, J. L., & van der Poel, S. (2017).
The International Glossary on Infertility and Fertility Care, 2017. Human Reproduction, 32(9), 1786–1801. https://doi.org/10.1093/humrep/dex234

5. Esteves, S. C., Roque, M., Bedoschi, G., Haahr, T., & Humaidan, P. (2018).
Intracytoplasmic sperm injection for male infertility and non-male factor infertility: Evidence-based practice. Andrology, 6(5), 735–742. https://doi.org/10.1111/andr.12515

6. Gardner, D. K., Weissman, A., Howles, C. M., & Shoham, Z. (2020).
Textbook of assisted reproductive techniques: Laboratory and clinical perspectives (5th ed.). CRC Press.

7. European Society of Human Reproduction and Embryology (ESHRE). (2021).
ESHRE guideline on male infertility.

Reproduction, 32(9), 1786–1801.

Esteves, S. C., et al. (2018).
Intracytoplasmic sperm injection for male infertility and non-male factor infertility: Evidence-based practice. Andrology, 6(5), 735–742.

Gardner, D. K., et al. (2020).
Textbook of Assisted Reproductive Techniques: Laboratory and Clinical Perspectives (5th ed.). CRC Press.

European Society of Human Reproduction and Embryology (ESHRE). (2021).
ESHRE guideline on male infertility.