One in seven UK couples struggle to conceive, and for 30% of them, standard tests reveal no obvious cause—leaving them with IVF as the only NHS treatment option, at roughly £5,000 per attempt. The UNITY Trial directly compares three cycles of a cheaper, less invasive alternative—intrauterine insemination (IUI), where sperm are placed directly into the uterus—against one cycle of IVF for couples with unexplained infertility. Current evidence on IUI’s effectiveness is uncertain, and no large UK trial has settled the question. This study will randomise 942 couples across diverse ethnic, social, and economic backgrounds, measuring live birth rates after 34 weeks of gestation. If IUI proves as effective as IVF for these couples, the impact could be substantial: a less physically demanding treatment option at lower cost to the NHS and patients, potentially freeing up resources for other fertility care. The trial also includes economic analysis, ethical assessments, and quality checks on sperm analysis—a notoriously variable diagnostic step. By including both NHS and privately funded couples, the results will reflect real-world UK healthcare provision and could reshape national treatment guidelines for unexplained infertility.
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Infertility, defined as the failure to conceive after 12 months or more of regular unprotected sex, affects 1 in 7 couples in the UK. Unexplained infertility (UEI) is when tests and investigations do not find an obvious cause, affecting about 30% of all infertile couples. The current UK treatment for UEI is in vitro fertilisation (IVF). Whilst IVF can overcome unexplained infertility in some couples, it is an invasive and expensive treatment, with associated procedures having potential side-effects and costing around £5000 per attempt. A less invasive, cheaper, alternative treatment is intrauterine insemination (IUI), where sperm are inserted into the uterus, increasing the chance of a sperm fertilising the egg. Although several international studies have suggested that IUI may be more cost effective than IVF, limitations and uncertainties in the current evidence mean there is a need for a large multicentre trial to provide rigorous evidence evaluating IUI treatment versus IVF for unexplained infertility. To address this question of whether 3 cycles of IUI is an appropriate alternative to one cycle of IVF for couples with UEI, in the ethnically, socially and economically diverse UK population, we have designed the UNITY Trial – UNexplained InfertiliTY treatment Trial. This multi-centre, multi-specialism trial will provide the rigorous evidence required to evaluate these treatment options; assessing value for money, feasibility, safety, appropriateness, and patient and ethical acceptability throughout the process. Patient and Public involvement will incorporate multilingual social media and infographic strategies to ensure the widest-possible audience and impact. The primary outcome measurement for the UNITY Trial will be the rate of Live Birth at >34 weeks gestation, assessed over a cohort sample size of 942 couples who will be randomised to one of the two treatment options. In addition, we will explore: the feasibility, acceptability, ethical implications and context of the interventions; perform an economic evaluation of the relative cost-effectiveness of each intervention from a healthcare perspective; develop suitable quality assurance procedures for assessing the male partner, as we know sperm analysis results to be variable internationally; and address the potential ethical, health equity and equality concerns regarding access to the trial and the proposed intervention. Crucially, we will take couples who are both NHS and privately funded, ensuring that we reflect the reality of healthcare provision in the UK. Results of the trial will inform future best practice and funding guidelines for treatment across the UK and beyond. Data from our ethnically, socially and economically diverse study participants will also inform future strategies for how all areas of society are educated and supported in fertility issues. Finally in performing consistency checks across our centres, via video-capture of the sperm sample, we also hope to validate video-based emerging technologies for sperm diagnostics that may better predict treatment success.
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