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Is One IVF Cycle Better Than Four IUIs? What 31% vs 55% Means

ByLife Choice Note

Short answer: In the randomized FIIX trial of 737 couples with unexplained infertility, the cumulative live-birth rate during the first seven months was 31% with up to four cycles of ovarian-stimulation intrauterine insemination (IUI) and 55% with one complete cycle of in vitro fertilization (IVF). After couples without a live birth or ongoing pregnancy could receive additional IVF, the cumulative rates through 20 months were 70% and 71%. The study therefore suggests that first-line IVF produced live births sooner in this setting; it does not show that every couple should skip IUI.

  • Publication date: October 27, 2026
  • Setting: Multicentre trial in New Zealand
  • Participants: 737 couples with unexplained infertility
  • Initial comparison: Up to four stimulated IUI cycles versus one complete IVF cycle
  • Not directly covered: Infertility with an identified cause, couples outside the trial’s age limits, or costs and coverage in other health systems

What exactly does 31% versus 55% compare?

The investigators assigned 365 couples to an IUI-first strategy and 372 to first-line IVF. The primary analysis included 585 couples after excluding those whose initial treatment stage occurred during COVID-19 lockdowns. Live births counted when the treatment cycle—or the last menstrual period leading to conception—started within seven months of randomization.

There were 89 live births among 288 couples in the IUI analysis group (31%) and 164 among 297 in the IVF group (55%). The adjusted risk difference was −24 percentage points for IUI, with a 95% confidence interval from −31 to −16 percentage points.

What does “not noninferior” mean?

The trial was designed to test whether the IUI-first result was no more than 10 percentage points worse than IVF. The observed difference and its confidence interval crossed that margin by a wide amount, so four stimulated IUI cycles did not meet the prespecified noninferiority criterion against one complete IVF cycle.

Failure to show noninferiority is not a universal instruction that IVF is best for every person. It addresses a defined strategy, population, time window, and outcome: cumulative live birth from treatment begun during the first seven months.

Why were the 20-month rates 70% and 71%?

Couples without a live birth or ongoing pregnancy after the first stage could proceed to stage 2. The IUI-first group could receive up to two IVF cycles, while the IVF-first group could receive one additional IVF cycle. Across treatment begun within 20 months, there were 257 live births among 365 couples in the IUI-first group (70%) and 265 among 371 in the IVF-first group (71%). The adjusted difference was 0 percentage points, with a 99% confidence interval from −9 to 8.

The seven-month comparison is therefore most informative about reaching a live birth sooner. The later result shows that a stepped strategy beginning with IUI can approach a similar overall rate when IVF is available after unsuccessful IUI. Because stage 2 involved treatment crossover, it is not a long-term comparison of IUI alone with IVF alone.

What counts as one complete IVF cycle?

A complete IVF cycle is not simply one embryo transfer. It includes one ovarian-stimulation and egg-retrieval episode followed by use of the embryos created in that retrieval, including eligible fresh and frozen transfers. The IUI strategy involved ovarian stimulation and insemination for up to four cycles. The procedures differ in time, invasiveness, monitoring, cost, and risk, so the percentages do not settle the choice by themselves.

What did the trial report about safety?

Serious adverse events occurred in six couples assigned to IUI first and 14 assigned to IVF first. Most were related to egg retrieval or ovarian hyperstimulation. The event numbers were small, and the trial was not designed to establish a precise safety difference, so 6 versus 14 should not be treated as a general risk estimate.

Who should be cautious about applying the result?

The registry limited enrollment to women younger than 39 years 4 months and men younger than 54 years 4 months. Couples with blocked fallopian tubes, a clear ovulatory disorder, severe male-factor infertility, or another identified cause may need a different treatment pathway. Ovarian reserve, previous attempts, miscarriage history, desired family size, multiple-pregnancy risk, affordability, and waiting time also matter.

This was a New Zealand trial. It did not evaluate insurance coverage, out-of-pocket cost, embryo-transfer policy, or access in South Korea, the United States, or other systems. It should not be used as an instruction to stop IUI or begin IVF without individualized fertility assessment.

Important limitations

  • The seven-month primary analysis included 585 of the 737 randomized couples because those treated during COVID-19 lockdowns were excluded.
  • The 20-month result includes subsequent IVF in the IUI-first group and is not an IUI-only outcome.
  • Failure of noninferiority does not prove IVF superiority for every patient or every outcome.
  • Cost, treatment burden, preferences, and country-specific access were not resolved by the live-birth percentages.
  • The findings cannot automatically be generalized beyond the age limits and unexplained-infertility definition used in the trial.

Primary sources

Written by: Life Choice Note — an independent personal health-information explainer based on the original study and trial registry.
Reviewed: November 2, 2026
Notice: This article provides general information and does not direct an individual choice between IUI and IVF. Discuss age, test results, previous treatment, risks, timing, and cost with a fertility specialist.

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