Recurrent implantation failure: reality or a statistical mirage?

Abstract

Importance: to date, recurrent implantation failure (RIF) has no clear definition and no clearly identified impaired function. Hence, the term RIF is currently used somewhat haphazardly, on the basis of clinicians' judgment. Objective: international experts in reproductive medicine met on July 1, 2022, in Lugano, Switzerland, to review the different facets of RIF and define the diagnosis and its appropriate management. Evidence review: a systematic review without meta-analysis of studies published in English from January 2015 to May 2022. Findings: data indicated that RIF has been largely overevaluated, overdiagnosed, and overtreated without sufficient critical assessment of its true nature. Our analyses show that true RIF is extremely uncommon-occurring in <5% of couples with infertility-and that reassurance and continued conventional therapies are warranted in most cases of assisted reproductive technology (ART) failure. Although the true biologic determinants of RIF may exist in a small subset of people with infertility, they elude the currently available tools for assessment. Without identification of the true underlying etiology(ies), it is reasonable not to assign this diagnosis to a patient until she has failed at least 3 euploid blastocyst transfers (or the equivalent number of unscreened embryo transfers, adjusted to the patient's age and corresponding euploidy rate). In addition, other factors should be ruled out that may contribute to her reduced odds of sustained implantation. In such cases, implantation failure should not be the only issue considered in case of ART failure because this may result from multiple other factors that are not necessarily repetitive or persistent. In reality, RIF impacting the probability of further ART success is a very rare occurrence. Conclusion: true RIF is extremely uncommon, occurring in <5% of couples with infertility. Reassurance and continued conventional therapies are warranted in most cases. It would seem reasonable not to assign this diagnosis to a patient until she has failed at least 3 euploid embryo transfers (or the equivalent number of unscreened embryos, adjusted to her age). Relevance: given the number of internationally recognized experts in the field present at the Lugano meeting 2022, our publication constitutes a consensus statement.