ICSI (Intracytoplasmic Sperm Injection) Guide: Indications, Success Rates & What to Expect

Key Takeaways: ICSI resolves the vast majority of fertilization failures caused by male infertility by injecting a single sperm directly into each egg under a microscope; it now accounts for more than 70% of IVF cycles worldwide and is the standard technique for any case involving significant male factor infertility. AddBaby Medical Group's partner fertility centers in Thailand use state-of-the-art microinjection systems achieving ICSI fertilization rates consistently above 75%, and offer integrated ICSI + TESE (surgical sperm retrieval) programs for even the most complex male infertility cases.

Quick Reference

Feature	Conventional IVF	ICSI
Fertilization method	Co-incubation of eggs and sperm	Single sperm microinjected into each egg
Sperm quantity required	Millions (for insemination)	Just 1 per egg
Average fertilization rate	60–70%	70–80%
Complete fertilization failure rate	~5–10%	~1–3%
Suitable for severe male factor	No	Yes
Compatible with PGT genetic testing	Only with ICSI	Fully compatible
Additional cost (estimate, Thailand)	—	~RMB 1,500–3,000 / cycle

---

Part 1: What Is ICSI and How Does It Differ from Conventional IVF?

The Limitation of Conventional IVF

In a conventional IVF cycle, retrieved eggs are placed in culture medium alongside hundreds of thousands of processed sperm, relying on the sperm's natural motility to penetrate the egg's zona pellucida and achieve fertilization. This process requires sperm to have reasonable numbers and swimming ability. When sperm parameters are severely compromised, natural fertilization may simply fail to occur — wasting an entire egg retrieval cycle.

The ICSI Revolution

In 1992, Palermo and colleagues at Ghent University in Belgium achieved the first successful pregnancy and birth using ICSI. The technique fundamentally changed the outlook for men with severe infertility: as long as at least one living sperm can be retrieved — from semen or through surgical extraction — fertilization becomes achievable regardless of sperm count or motility.

The ICSI procedure step by step:

1. Sperm selection: An embryologist selects morphologically normal, motile sperm from the semen sample or surgically retrieved material under high-power microscopy.
2. Egg immobilization: A mature MII-stage egg (having completed the first meiotic division) is gently held in place with a holding pipette.
3. Microinjection: Using an injection needle approximately 6–7 micrometers in diameter (far thinner than a human hair), a single sperm is aspirated and injected directly through the zona pellucida into the egg's cytoplasm.
4. Post-injection culture: Injected eggs are returned to the incubator. After 16–18 hours, fertilization is confirmed by the presence of two pronuclei (2PN), after which the embryo proceeds to standard culture.

The entire procedure is performed on a fully automated micromanipulation platform by an experienced embryologist, with each egg taking approximately 2–3 minutes.

---

Part 2: Who Should Use ICSI? A Detailed Analysis of Indications

ICSI is not required for all IVF patients, but is strongly recommended for the following groups:

1. Severe Oligospermia (Very Low Sperm Count)

The WHO defines oligospermia as a sperm concentration below 15 million/mL, and severe oligospermia as below 5 million/mL. Conventional IVF fertilization rates in severe oligospermia are extremely low; ICSI brings fertilization rates up to levels comparable to normal semen.

2. Severe Asthenospermia (Very Low Sperm Motility)

When the proportion of progressively motile sperm (PR) falls below 10%, the sperm are essentially unable to penetrate the zona pellucida independently. ICSI bypasses this physical barrier entirely.

3. Obstructive Azoospermia (OA) — PESA/MESA + ICSI

Obstructive azoospermia occurs when the testes produce sperm normally but the delivery pathway is blocked (congenital bilateral absence of the vas deferens, infection, prior vasectomy, or surgical scarring). Sperm are retrieved surgically:

• PESA (Percutaneous Epididymal Sperm Aspiration): A needle is inserted into the epididymis under local anesthesia — minimally invasive.
• MESA (Microsurgical Epididymal Sperm Aspiration): The epididymis is directly opened under a microscope for higher-yield, more consistent retrieval. Retrieved sperm are used directly for ICSI, achieving fertilization rates comparable to ejaculated sperm.

4. Non-Obstructive Azoospermia (NOA) — TESE/Micro-TESE + ICSI

NOA involves impaired spermatogenesis in the testes, but focal islands of sperm production may still exist. Surgical retrieval options include:

• TESE (Testicular Sperm Extraction): Multiple testicular biopsies are taken to locate sperm.
• Micro-TESE (Microdissection TESE): The most successful retrieval technique, using a surgical microscope to identify swollen, sperm-producing seminiferous tubules for targeted sampling. Sperm retrieval rates of 40–60% have been reported (approximately 50% in Klinefelter syndrome). Retrieved sperm are either immediately frozen or used fresh for ICSI.

5. Prior IVF Fertilization Failure or Very Low Fertilization Rate

If a previous conventional IVF cycle produced a fertilization rate below 30% or complete fertilization failure, ICSI is recommended in the subsequent cycle.

6. Use of Frozen-Thawed Sperm

The freeze-thaw process causes some motility loss. ICSI is recommended when using cryopreserved sperm to safeguard fertilization rates.

7. Severe Teratospermia (Severely Abnormal Sperm Morphology)

Isolated teratospermia has limited impact on ICSI versus conventional IVF outcomes, but when combined with low count or motility, ICSI provides greater reliability.

8. Preimplantation Genetic Testing (PGT) — ICSI Is Mandatory

PGT-A (aneuploidy screening), PGT-M (monogenic disease testing), and PGT-SR (structural rearrangements) all require ICSI rather than conventional IVF. The reason: PGT involves biopsying cells from the blastocyst; with conventional IVF, residual sperm DNA adhering to the egg's outer surface could contaminate the biopsy sample and compromise genetic analysis accuracy. ICSI eliminates this contamination risk.

---

Part 3: ICSI Success Rates and What Determines Outcomes

Fertilization Rate Data

Clinical data consistently show:

• ICSI average fertilization rate: 70–80% (approximately 7–8 of every 10 injected eggs fertilize successfully)
• Conventional IVF average fertilization rate: 60–70%
• ICSI complete fertilization failure rate: Approximately 1–3% (rare, usually due to egg quality issues)

The Primary Determinant: Egg Quality

This is a critical point that many patients overlook. ICSI solves the problem of "whether sperm can enter the egg." However, what happens after fertilization — the speed of cell division, the rate of blastocyst formation, and crucially, the chromosomal normality rate — is primarily determined by egg quality, not sperm quality.

Put plainly: even with ICSI and the best available sperm, if the female partner has diminished ovarian reserve (low AMH, low antral follicle count) or poor egg quality due to advanced maternal age, embryo development rates and pregnancy rates will still be limited. This is why AddBaby recommends a comprehensive fertility assessment and, for women with advanced age or reduced ovarian reserve, consideration of PGT-A to select chromosomally normal embryos. Learn more about our fertility assessment and IVF services.

The Role of Sperm DNA Fragmentation Index (DFI)

The DNA Fragmentation Index (DFI) reflects the integrity of sperm genetic material. When DFI exceeds 25%, even successful ICSI fertilization may be followed by reduced embryo developmental potential and higher early miscarriage rates. For patients with high DFI, AddBaby recommends:

• PICSI (Physiological ICSI, see below) for superior sperm selection
• Antioxidant therapy to improve sperm DNA quality before cycling
• Testicular sperm ICSI (TESE-ICSI): Testicular sperm typically has significantly lower DFI than ejaculated sperm

---

Part 4: AddBaby's ICSI + TESE Integrated Programs

For male infertility patients, AddBaby offers comprehensive, individualized solutions covering the full pathway from semen evaluation to ICSI fertilization. Contact our reproductive consultants to build your personalized treatment plan.

Urology-Reproductive Medicine Joint Consultation

AddBaby's partner hospitals in Thailand — including leading Bangkok centers such as SAFE Fertility Center and BNH Hospital — offer integrated urology-reproductive medicine clinics for azoospermia patients. Urological surgeons assess surgical feasibility and perform sperm retrieval, while embryologists simultaneously prepare the eggs for ICSI. This coordinated approach maximizes the use of every precious surgically retrieved sperm.

Same-Day Retrieval Coordination

For patients undergoing surgical sperm retrieval (PESA/MESA/TESE), AddBaby coordinates the surgical retrieval with the female partner's egg retrieval on the same day, avoiding quality degradation from time delays and maximizing fertilization rates in fresh cycles.

Sperm Cryopreservation Banking

For patients with successful surgical retrieval, AddBaby can arrange sperm cryopreservation at accredited Thai sperm banks as a backup for future cycles, eliminating the need for repeated surgical procedures and their associated costs and risks.

PICSI (Physiological ICSI) — Enhanced Sperm Selection

PICSI is an enhanced version of standard ICSI that incorporates an additional sperm selection step. The technique uses hyaluronic acid (a natural glycoprotein secreted by the egg) as a binding test — mature sperm with intact DNA have a significantly stronger affinity for hyaluronic acid than sperm with DNA fragmentation. PICSI-selected sperm have substantially lower DFI and are particularly beneficial for:

• Patients with DFI > 25%
• Patients with poor previous embryo quality or recurrent miscarriage
• Advanced maternal age cases or cycles with low euploid embryo rates

Learn more about our complete ICSI and male infertility treatment options or contact AddBaby for a free online consultation.

---

Frequently Asked Questions (FAQ)

Q1: Does ICSI affect the health of children born this way?

A: Long-term follow-up studies involving large cohorts have not found significant differences in overall health, intellectual development, or congenital anomaly rates between children born through ICSI and those born through natural conception or conventional IVF. One consideration worth noting: ICSI may transmit paternal genetic factors related to infertility — for example, Y-chromosome microdeletions associated with severe oligospermia — to male offspring. However, this represents natural inheritance of existing genetic information, not a new risk introduced by the ICSI procedure itself.

Q2: Does every IVF cycle need ICSI?

A: No. For patients with normal semen parameters, no prior fertilization failure, and no requirement for PGT genetic testing, conventional IVF is typically sufficient and ICSI is not necessary. The decision to use ICSI is made by the reproductive specialist based on semen analysis results and treatment history, not as a default for all patients.

Q3: Does azoospermia always require surgical sperm retrieval?

A: For obstructive azoospermia (e.g., congenital bilateral absence of the vas deferens, post-vasectomy), surgical retrieval (PESA/MESA) is typically the first-line approach. Non-obstructive azoospermia requires more extensive evaluation — including hormonal testing and genetic analysis (Y-chromosome microdeletion panel, karyotype) — to determine whether focal spermatogenesis exists before deciding whether TESE/Micro-TESE is appropriate. Some NOA patients respond to hormonal stimulation therapy and subsequently produce sperm in their ejaculate, eliminating the need for surgery.

Q4: How much more does ICSI cost compared to conventional IVF?

A: At Thai fertility centers, ICSI typically adds approximately RMB 1,500–3,000 (around 7,000–15,000 THB) to the base IVF cost, covering the embryologist's micromanipulation fee. Given the significantly higher fertilization rates and dramatically reduced risk of complete fertilization failure, ICSI represents strong value for money for patients with appropriate indications.

---

Summary

Since its introduction in 1992, ICSI has helped millions of families worldwide overcome male infertility to achieve pregnancy. From severe oligospermia and asthenospermia to complete azoospermia requiring surgical retrieval, from prior fertilization failure to mandatory PGT genetic testing, ICSI has become the defining technique of modern IVF.

AddBaby Medical Group partners with Thailand's leading fertility centers to provide comprehensive ICSI programs — including PICSI for enhanced sperm selection, Micro-TESE for non-obstructive azoospermia, and fully coordinated same-day retrieval protocols. Contact AddBaby today to begin your personalized fertility assessment, and explore our complete IVF service offerings.

---

Reviewed by the AddBaby Medical Group clinical team. Last updated: February 2026