What Is IUI and How Is It Different From IVF?

IUI and IVF are two of the most commonly mentioned fertility treatments — and they are frequently confused, combined, or treated as if one automatically leads to the other. They are, in fact, quite different procedures with different indications, different success rates, and different levels of intervention.

Here is a plain-language explanation of both, and how to think about which might apply to your situation.

What Is IUI?

IUI stands for Intrauterine Insemination. It is a relatively simple procedure in which sperm — either from the male partner or a donor — is prepared in a laboratory and then placed directly into the uterus around the time of ovulation.

The key thing IUI does is reduce the distance sperm has to travel. In natural conception, sperm must travel from the vagina through the cervix and into the uterus to reach the fallopian tube. IUI bypasses the cervical step, placing processed sperm directly into the uterus.

IUI does not bypass the fallopian tubes. For fertilisation to occur after IUI, the sperm must still travel through the tube to meet the egg. This means IUI is not appropriate for women with blocked fallopian tubes.

IUI can be done in a natural cycle (timed to natural ovulation) or with mild ovarian stimulation (to produce one or two follicles and improve timing precision). The stimulation used in IUI is mild compared to IVF.

What Is IVF?

IVF stands for In Vitro Fertilisation. It involves stimulating the ovaries to produce multiple eggs, retrieving those eggs through a minor procedure under sedation, fertilising them with sperm in a laboratory, and then transferring one or more resulting embryos into the uterus.

IVF is more intensive than IUI in every respect: more medication, more monitoring, a retrieval procedure, laboratory embryology, and then the transfer. It is also more expensive.

The key thing IVF does is bypass the fallopian tubes entirely. Eggs are retrieved directly from the ovaries and fertilised externally. Whether the tubes are open, blocked, or absent is irrelevant to the IVF process.

The Key Differences

| | IUI | IVF | |---|---|---| | Where fertilisation occurs | Inside the body (in the tube) | In the laboratory | | Fallopian tubes required | Yes | No | | Stimulation intensity | Mild (1–2 eggs) | Significant (multiple eggs) | | Sperm preparation | Yes | Yes | | Invasive procedure | No | Yes (egg retrieval) | | Cost | Lower | Higher | | Success rate per cycle | 10–20% (approximate) | 30–45% under 35 (approximate) |

When Is IUI Used?

IUI is typically considered when:

• Mild male factor: Sperm count or motility is slightly below normal, but not severely impaired. Placing processed sperm closer to the egg improves the chances per cycle.
• Unexplained infertility in younger women: Where all investigations are normal but conception is not occurring after a reasonable period of trying.
• Cervical factor: Where the cervical environment may be hostile to sperm.
• Ovulation induction support: When a woman is using medication to induce ovulation and IUI is added to improve timing and sperm delivery.
• Donor sperm: When a couple is using donor sperm, IUI is the first-line delivery method.

IUI is not recommended when:

• Fallopian tubes are blocked or severely damaged
• AMH is significantly low and ovarian response is unlikely to be adequate
• Male factor is severe (very low count or very poor motility)
• The woman is significantly older and the per-cycle success rate of IUI is unlikely to justify the time spent

When Is IVF Used?

IVF is recommended when:

• Fallopian tubes are blocked or absent: IVF is the only option when the tubes cannot be used.
• Severe endometriosis: Particularly when structural damage is extensive.
• Significant male factor: Very low sperm count or very poor motility that makes IUI unlikely to succeed.
• IUI has failed: After two to four IUI cycles without success, IVF is typically recommended as the next step.
• Low ovarian reserve: Where the window is shorter and the per-cycle efficiency of IVF makes more clinical sense.
• Genetic testing needed: IVF allows for pre-implantation genetic testing (PGT) of embryos before transfer.

Frequently Asked Questions

Q: Do I have to try IUI before IVF? A: No — this is a common misconception. IUI is not a mandatory step on the way to IVF. Whether IUI or IVF is the appropriate starting point depends on your specific situation: your age, your test results, your partner's semen analysis, and your medical history. For some couples, IVF is the logical first treatment; for others, IUI makes sense first.

Q: Is IUI painful? A: Most women describe IUI as similar to a cervical smear — a brief discomfort rather than pain. The procedure takes a few minutes and most women return to normal activity immediately afterward.

Q: How many IUI cycles should I try before moving to IVF? A: Most specialists recommend two to four IUI cycles before moving to IVF, assuming the indication for IUI is appropriate. After that, the cumulative time and emotional cost of continued IUI typically makes IVF the better investment.

Q: Does IUI with stimulation increase the risk of twins? A: Yes — mild stimulation for IUI can produce two or occasionally three follicles, which increases the risk of multiple pregnancy. Your doctor will monitor the cycle carefully and may cancel or convert it if the response is too high.

Q: Can I have IUI if my partner has a low sperm count? A: It depends on how low. IUI with mild male factor can be effective. With severely low count or very poor motility, IVF with ICSI (where a single sperm is injected directly into the egg) is typically recommended instead.

A free fertility assessment helps map which of these options — natural trying, IUI, or IVF — makes most sense for your specific situation based on both partners' investigations.