TL;DR
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In a New Zealand randomized trial of couples with unexplained infertility, 55% assigned to IVF had a live birth by seven months, compared with 31% assigned to IUI first. By 20 months, after IUI patients could proceed to IVF, rates were similar: 71% for direct IVF and 70% for the IUI-first strategy.
A multicenter randomized trial in New Zealand found that couples with unexplained infertility assigned to start with in vitro fertilization (IVF) were more likely to have a live birth within seven months than couples assigned to start with intrauterine insemination (IUI). By 20 months, after the IUI-first group could move on to IVF, cumulative live-birth rates were similar, suggesting the initial strategy affected how quickly births occurred more than the overall chance of a live birth over the trial period.
The Fertility and IVF and IUI Trial for Unexplained Infertility, known as FIIX, enrolled 737 couples at six fertility clinics in New Zealand between August 2019 and March 2024. The final analysis included 288 couples assigned to IUI first and 297 assigned to IVF first. Participants had a mean maternal age of 34.3 years.
At seven months, the cumulative live-birth rate was 31% in the IUI-first group and 55% in the IVF-first group. The adjusted risk difference was minus 24 percentage points for IUI compared with IVF, with a 95% confidence interval from minus 31 to minus 16. The trial’s primary analysis tested whether IUI was noninferior to IVF at that point; the researchers said it was not.
The treatment pathways changed after the seven-month assessment. Couples in the IUI group could receive up to four IUI cycles with oral ovarian stimulation, then up to two IVF cycles if they had not had a live birth. The IVF group received one IVF cycle, including transfer of all embryos, and could proceed to another IVF round after seven months if needed. At 20 months, live-birth rates were 70% for the IUI-first strategy and 71% for direct IVF. Researchers reported six serious adverse events in the IUI group and 14 in the IVF group; most in the IVF group were related to egg retrieval or ovarian hyperstimulation.
How Treatment Order Affected Timing
The findings distinguish speed to live birth from the chance of eventually having a live birth across the study period. For couples who place a high priority on reaching a pregnancy sooner, the seven-month difference may matter. But the similar 20-month rates indicate that starting with IUI did not appear to lower the cumulative rate once participants who needed further treatment could access IVF.
The decision also involves cost, access, treatment burden, and safety. IVF is generally a more intensive and expensive treatment, and insurance coverage varies. IUI may be less invasive and more affordable for some patients, while others may have coverage or clinical circumstances that favor IVF first. The trial measured outcomes under its specific treatment pathways; it does not establish that one approach is the best choice for every couple.
Study co-author Lucy Prentice of the University of Auckland said the findings could affect practice and said the trial directly compared the two strategies. The authors argued that guideline recommendations placing IUI before IVF may warrant reconsideration. That is a research interpretation, not a change in clinical guidance established by the trial itself.
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Why the Trial Compared First Treatments
For unexplained infertility, clinicians may recommend a sequence of IUI with ovarian stimulation followed by IVF if pregnancy does not occur. The trial examined that staged approach against going directly to IVF, rather than comparing only isolated treatment cycles. Its 20-month results reflect the fact that couples assigned to IUI could later receive IVF, making the final figures a comparison of treatment strategies over time.
Prentice and colleagues wrote that IUI with ovarian stimulation did not meet the noninferiority standard at the seven-month stage. They also cautioned that decisions should account for cost-effectiveness, access, patient preferences, treatment burden and safety. Rachel Weinerman, a reproductive endocrinologist at Case Western Reserve University who was not involved, said current recommendations to try IUI before IVF remain reasonable because the cumulative live-birth rates were similar when unsuccessful IUI was followed by IVF. She said she would continue to recommend three IUI cycles followed by IVF for many patients, while noting that direct IVF can be reasonable when insurance coverage favors it.
The researchers said international guidance supporting IUI first has relied in part on studies showing a benefit over expectant management, rather than strong direct comparisons with IVF. Their trial adds a randomized comparison, but its results apply to the study’s participants and treatment protocol.
“Our finding that IUI with ovarian stimulation was not noninferior to IVF in stage 1 calls into question current international guideline recommendations.”
— Lucy Prentice, University of Auckland study co-author
Limits of the Evidence
The study used a broad definition of unexplained infertility, and the researchers said its results may not apply to couples whose infertility had lasted for a shorter period. They also said some participants may have had undiagnosed endometriosis. Because patients and clinicians could not be blinded to the treatments, expectations or care decisions may have affected aspects of the trial.
The COVID-19 pandemic disrupted the study. Researchers changed the protocol and analyses, excluded couples who were in the first stage during lockdown, and increased the planned sample size. The supplied report does not provide subgroup results that would establish which patient characteristics most affect the choice between IUI and IVF, nor does it settle how the strategies compare in settings with different costs, insurance rules or access to fertility services.
The trial reported the number of serious adverse events in each group and said most IVF-group events were related to egg retrieval or ovarian hyperstimulation. Those counts do not, by themselves, explain each patient’s risk or establish how the safety balance would look under other protocols. The findings should be discussed with a qualified fertility specialist in light of individual circumstances.
Guidelines and Clinical Decisions
The trial authors said their results may prompt a review of guidelines that recommend IUI before IVF. The study does not itself revise those recommendations, and the source report did not identify a scheduled guideline review or a timeline for one.
For now, the practical decision remains a discussion between patients and their clinicians. Couples may weigh the earlier live-birth rate observed with IVF against the cost, availability, invasiveness and preferences associated with each route. Further research and guideline reviews may clarify how well these results apply to different patient groups and health-care systems. The central finding remains specific: IVF first was associated with more live births by seven months, while the two trial strategies had similar cumulative rates by 20 months after IVF became available to the IUI-first group.
Key Questions
What did the trial find at seven months?
Fifty-five percent of couples assigned to IVF first had a live birth by seven months, compared with 31% assigned to IUI first.
Were the live-birth rates still different at 20 months?
No. By 20 months, the reported cumulative rates were 70% for the IUI-first strategy and 71% for direct IVF. The IUI group could proceed to IVF after the seven-month stage if needed.
Does the study mean all couples should start IVF?
No. The trial compared treatment strategies in couples with unexplained infertility, but treatment choices also depend on factors such as cost, insurance coverage, access, patient preferences and clinical circumstances. A fertility specialist can discuss how the findings apply to an individual couple.
Who took part in the FIIX trial?
The trial randomized 737 couples across six fertility clinics in New Zealand from August 2019 to March 2024. The final analysis included 288 couples in the IUI group and 297 in the IVF group.
What limitations did the researchers report?
They said the broad definition of unexplained infertility may limit how widely the findings apply, and some participants may have had undiagnosed endometriosis. The pandemic also led to changes in the protocol and analyses, and the treatments could not be blinded.
Source: medpagetoday.com
