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Going straight to IVF gets couples to a live birth faster than starting with intrauterine insemination (IUI), a large New Zealand trial found. But by 20 months, cumulative live birth rates were nearly identical between the two groups. Experts say cost, insurance coverage, and patient preference should still guide the choice of first-line fertility treatment.
Couples with unexplained infertility who went straight to IVF achieved live births significantly faster than those who started with intrauterine insemination (IUI), according to the FIIX trial — the largest head-to-head comparison of the two approaches to date. Published in the New England Journal of Medicine and presented at the ASRM annual meeting, the multicenter randomized controlled trial followed 585 couples across six New Zealand fertility clinics.
The gap, however, narrowed considerably over time. Once IUI patients were offered IVF in the trial's second stage, cumulative live birth rates evened out — suggesting that starting with IUI doesn't close the door on a successful pregnancy, just delays it.
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Why it matters: These findings challenge current international guidelines that recommend IUI before IVF. While IVF is faster and more effective upfront, IUI remains a reasonable, less invasive, and often cheaper first step — especially for patients without insurance coverage for IVF. Clinicians and patients now have stronger evidence to weigh both paths based on individual circumstances.
