摘要：Objective: The aim of the stud. was to propose a set of tests to clarify the d.agnosis of repeated.implantation failure in patients und.rgoing in vitro fertilization (IVF). Stud. d.sign: Fifty-nine patients with at least two unsuccessful IVF attempts were includ.d.in the stud.. Blood.samples were evaluated.for the presence of und.rlying thyroid.abnormalities, antiphospholipid.antibod.es (aPL), increased.levels of natural killer cells (NK), inherited.thrombophilia and.mouse embryo assay factor (MEAf). The same tests were performed.on 20 normal fertile control patients. Results: Seventy-six percent of IVF patients showed.at least one abnormal result. This incid.nce was higher with respect to that found.among control patients (45% ). The prevalence of thyroid.abnormalities, aPL and.increased.NK level was higher in IVF patients whereas no d.fferences were observed.in terms of prevalence of inherited.thrombophilias and.MEAf. Conclusions: A better und.rstand.ng of reprod.ctive failure mechanisms should.allow an effective d.agnostic flow chart and.a focused.therapeutic option for patients experiencing repeated.IVF failure. With this objective in mind. our d.ta provid. two important results: thyroid.abnormalities, aPL and.increased.NK levels are more prevalent in women experiencing IVF failure. No evid.nce was found.for an association between inherited.thrombophilia and.MEAf and.failure to achieve pregnancy after IVF.