What exactly do we mean by ‘recurrent implantation failure’? A systematic review and opinion

Recurrent implantation failure (RIF) is an iatrogenic condition, being the result of repetitive unsuccessful cycles of IVF or intracytoplasmic sperm injection (ICSI) treatment. The aim of this review was to assess the definitions of RIF used in literature as well as suggest a uniform definition of this condition. A systematic search of MEDLINE, Embase and Cochrane Library was conducted. The most commonly stated definitions described RIF as ‘three or more failed treatment cycles’ or ‘two or more failed cycles’. Other identified definitions were based solely on the number of embryos transferred in previous cycles or combined the number of previously failed cycles with the number of transferred embryos. Several other definitions were also identified. This review highlights the lack of uniformity of the definition of RIF. Based on the available literature and the expert opinion of the authors, RIF should be defined as the absence of implantation after two consecutive cycles of IVF, ICSI or frozen embryo replacement cycles where the cumulative number of transferred embryos was no less than four for cleavage-stage embryos and no less than two for blastocysts, with all embryos being of good quality and of appropriate developmental stage.Recurrent implantation failure (RIF) is a condition resulting from repetitive unsuccessful cycles of IVF or intracytoplasmic sperm injection (ICSI) treatment. The aim of this review was to assess the definitions of RIF used in literature as well as suggest a uniform definition of this condition. A systematic search of MEDLINE, Embase and Cochrane Library was conducted. The most commonly stated definitions described RIF as ‘three or more failed treatment IVF or ICSI cycles’ or ‘two or more’ failed cycles. Other identified definitions were based only on the number of embryos transferred in previous cycles or combined the number of previously failed cycles with the number of transferred embryos. This review highlights the lack of consistency of the definition of recurrent implantation failure. Based on the available literature and the expert opinion of the authors, RIF should be defined as the absence of attachment of the embryo to the lining of the womb after two consecutive cycles of IVF, ICSI or frozen embryo replacement cycles where the cumulative number of transferred embryos was no less than four for day-2 embryos and no less than 2 for day-5 embryos (blastocysts), with all embryos being of good quality and of appropriate developmental stage. We hope that adopting a standard definition will allow for good-quality research to be conducted into this distressing condition preventing couples from having offspring.