ICSI: what it is and when it is needed
ICSI — intracytoplasmic sperm injection — means a single sperm is injected directly into an egg, rather than eggs and sperm being placed together as in conventional IVF.
When it is genuinely indicated
Significant male factor — low count, poor motility, or abnormal morphology sufficient that conventional fertilisation is unlikely.
Surgically retrieved sperm — where sperm come from the testis or epididymis, as in azoospermia, ICSI is necessary because numbers are limited.
Previous fertilisation failure with conventional IVF.
Where PGT is planned, to avoid contamination from surrounding sperm affecting the genetic result.
Where the case is weaker
ICSI is used far more widely than these indications require. In couples without male factor, it has not been shown to improve live birth rates over conventional IVF — and it costs more.
If ICSI is being recommended and there is no male factor, no previous fertilisation failure and no PGT planned, it is reasonable to ask what specifically it is expected to achieve in your case.
What ICSI does not do
It does not improve egg quality. It does not improve embryo quality beyond overcoming a fertilisation barrier. It does not increase the number of eggs retrieved.
It bypasses one specific step — sperm reaching and penetrating the egg. Everything downstream is unchanged.
Laboratory benchmarks
From the Vienna Consensus, for ICSI: the polyspermy rate should be under 6%, and the 1PN rate under 3% — lower than the under-5% expected for conventional IVF, because oocytes are pre-selected before injection.
Damage during the injection procedure is measured as a performance indicator. Ask your clinic for their figures.
Safety
ICSI has been in use for decades. Concerns have been raised about outcomes in children conceived this way, and the honest position is that ESHRE notes children born after assisted reproduction as singletons do differ in some respects from spontaneously conceived children — but whether that reflects the underlying infertility, the procedures, or both remains unclear.
Where ICSI is used for male factor with a genetic cause — a Y-chromosome microdeletion, for instance — that cause will be passed to male offspring. An AZFc deletion transmits to all sons, who will have the same fertility problem. This should be discussed before treatment.
What to ask
Why ICSI rather than conventional IVF in my case? What is your fertilisation rate with each? What is the additional cost?
Sources
- Vienna Consensus — ART laboratory performance indicators (2017)
Frequently Asked Questions
Is ICSI better than IVF?▾
ICSI and conventional IVF achieve the same live birth rates when sperm parameters are normal. For male factor infertility — low count, poor motility, or surgically retrieved sperm — ICSI significantly outperforms conventional IVF. ASRM 2023 recommends ICSI specifically for male factor indications, not routinely for all IVF where sperm are normal.
Does ICSI increase the risk of birth defects?▾
Large registry studies show ICSI is associated with a very small increase in imprinting disorders (Beckwith-Wiedemann, Angelman syndromes) — absolute risk approximately 0.5% vs 0.3% in natural conception. ICSI does not increase the risk of chromosomal abnormalities or most congenital defects. The benefit in treating male infertility far outweighs this very small risk.
What sperm count requires ICSI?▾
ICSI is recommended when total motile sperm count (TMSC) after preparation falls below 5 million, when progressive motility is below 10%, or when sperm are surgically retrieved. For TMSC between 5 and 20 million, either conventional IVF or ICSI may be appropriate depending on other factors.