IUI, IVF, ICSI: which procedure for which problem, and why clinics often skip the simpler option

Reviewed by HHH Clinical Team · April 2026

1 section · 2 min read

Fertility & Treatment

2 minHHH clinical team

SHOULD YOU DO IUI, IVF, OR ICSI?

Should you do IUI, IVF, or ICSI?

IUI, , and get blurred together in fertility-clinic conversations. They are not interchangeable. Each is built around a different obstacle in conception, and using the wrong one is either ineffective ( for a problem cannot solve) or unnecessarily invasive and expensive ( for a problem that does not need it). Knowing what each one is actually for makes a clinic conversation a different kind of conversation.

IUI, intrauterine insemination

Sperm is washed and concentrated, then placed directly into the uterus around ovulation. Solves: mild male factor, cervical issues, single parents and same-sex couples using donor sperm. Per-cycle success: 10 to 20 per cent under 35, lower with age. Cheaper, less invasive, no eggs collected.

IVF, in vitro fertilisation

Eggs are stimulated, collected, mixed with sperm in a dish, embryos selected and transferred. Solves: tubal factor (blocked or absent fallopian tubes), unexplained infertility after IUI failure, ovulation disorders not responding to simpler treatments, age-related decline. Per-cycle success: heavily age-dependent, around 30 to 40 per cent live birth under 35, declining with age.

ICSI, intracytoplasmic sperm injection

A single sperm is injected directly into each egg under a microscope. ICSI is added on to IVF; it is not a separate procedure. Solves: severe male factor (low count, low motility, abnormal morphology), failed fertilisation in previous IVF cycles, surgically retrieved sperm. For non-male-factor cases, ICSI does not improve live birth rates over conventional IVF.

The grey zone

Should I do IUI first or go straight to IVF?

Standard position · UK

UK NICE traditionally recommended IUI before IVF for unexplained subfertility, mild male factor, and mild endometriosis. The 2025 update has narrowed this, many subgroups now move to IVF more directly because IUI cycles in low-success groups effectively delay treatment without changing outcomes.

Where it gets more nuanced

What we honestly do not know

The optimal number of IUI cycles before moving to IVF for any given couple is not settled. Three is a common rule of thumb, supported by limited data. Whether ICSI add-on improves outcomes for borderline-male-factor cases is genuinely uncertain, it sits in the grey zone between clear ICSI indication and clear non-indication.

Bottom line

If you are under 35, have no significant risk factors, and the male partner has reasonable semen analysis, asking about IUI as a first step is reasonable. If you are over 38 or have known risk factors, asking why IUI rather than IVF is also reasonable. If a clinic is recommending ICSI without male-factor justification, ask for the reason, there often isn't a good one.

References

[1] 28333228Tjon-Kon-Fat RI et al. IVF or IUI as first-line treatment in unexplained subfertility: the conundrum of treatment selection criteria. Hum Reprod 2017;32(5):1028-1032.
[2] pmid-icsi-vs-ivf-non-male-factor-2021Geng T et al. Routine use of ICSI for non-male factor infertility: a systematic review and meta-analysis. Reprod Biol Endocrinol 2021.
[3] nice-cg156-fertility-2026NICE Clinical Guideline CG156: Fertility problems: assessment and treatment.

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For your doctor

Patient seeks fertility treatment escalation discussion. Requests review of IUI vs IVF first-line appropriateness given age, ovarian reserve, semen analysis, and any tubal factors. Discussion of whether ICSI is indicated.

I want to talk about whether IUI or IVF is the right starting point for me. Could we go through my age, ovarian reserve, partner's semen analysis, and tube assessment, and decide what's appropriate?

How did this land with you?