In Vitro Fertilization or Intrauterine Insemination in Unexplained Infertility.

October 27, 2026| Source: The New England journal of medicine

Although international guidelines recommend intrauterine insemination (IUI) with ovarian stimulation as first-line treatment for unexplained infertility, evidence from comparisons of this method with in vitro fertilization (IVF) is limited. We conducted a sequential, multicenter, randomized, controlled trial involving couples with unexplained infertility. Stage 1 was a noninferiority comparison between IUI with ovarian stimulation (up to four cycles) and IVF (one complete cycle, with transfer of all embryos). After 7 months, couples without live birth or ongoing pregnancy could proceed to stage 2: couples in the IUI group could undergo up to two IVF cycles, and those in the IVF group could undergo one further IVF cycle. The primary outcome was the cumulative live-birth rate resulting from stage 1. Couples who were in stage 1 during lockdowns due to coronavirus disease 2019 were omitted from the analysis of the primary outcome. A secondary outcome was the cumulative live-birth rate resulting from stages 1 and 2. Live births were included in analyses if day 1 of the treatment cycle that led to pregnancy or day 1 of the last menstrual period before conception occurred within 7 months (stage 1) or 20 months (stage 2) after randomization. The noninferiority margin for the primary outcome was a between-group difference of 10 percentage points. A total of 737 couples underwent randomization: 365 couples were assigned to undergo IUI with ovarian stimulation before IVF, and 372 were assigned to undergo first-line IVF (1 couple in the IVF group withdrew consent for the use of data). The primary-outcome analysis included 585 couples (288 in the IUI group and 297 in the IVF group). The cumulative live-birth rate from stage 1 was 31% (89 births among 288 couples) with IUI with ovarian stimulation and 55% (164 births among 297 couples) with IVF (adjusted risk difference, -24 percentage points; 95% confidence interval [CI], -31 to -16). The cumulative live-birth rate from stages 1 and 2 among all the couples who had undergone randomization and provided consent was 70% (257 births among 365 couples) and 71% (265 births among 371 couples), respectively (adjusted risk difference, 0 percentage points; 99% CI, -9 to 8). Overall, serious adverse events occurred in 6 couples in the IUI group and in 14 couples in the IVF group; most serious adverse events were related to oocyte retrieval or hyperstimulation. In couples with unexplained infertility, treatment with four cycles of IUI with ovarian stimulation was not noninferior to treatment with one complete cycle of IVF with respect to the cumulative live-birth rate. (Funded by the Health Research Council of New Zealand and others; FIIX Australian New Zealand Clinical Trials Registry number, ACTRN12619001003167.).

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