摘要：Obje.tive. The.aim of the.study was to propose.a se. of te.ts to clarify the.diagnosis of re.e.te. implantation failure.in patie.ts unde.going in vitro fe.tilization (IVF). Study de.ign: Fifty-nine.patie.ts with at le.st two unsucce.sful IVF atte.pts we.e.include. in the.study. Blood sample. we.e.e.aluate. for the.pre.e.ce.of unde.lying thyroid abnormalitie., antiphospholipid antibodie. (aPL), incre.se. le.e.s of natural kille. ce.ls (NK), inhe.ite. thrombophilia and mouse.e.bryo assay factor (Me.f). The.same.te.ts we.e.pe.forme. on 20 normal fe.tile.control patie.ts. Re.ults: Se.e.ty-six pe.ce.t of IVF patie.ts showe. at le.st one.abnormal re.ult. This incide.ce.was highe. with re.pe.t to that found among control patie.ts (45% ). The.pre.ale.ce.of thyroid abnormalitie., aPL and incre.se. NK le.e. was highe. in IVF patie.ts whe.e.s no diffe.e.ce. we.e.obse.ve. in te.ms of pre.ale.ce.of inhe.ite. thrombophilias and Me.f. Conclusions: A be.te. unde.standing of re.roductive.failure.me.hanisms should allow an e.fe.tive.diagnostic flow chart and a focuse. the.ape.tic option for patie.ts e.pe.ie.cing re.e.te. IVF failure. With this obje.tive.in mind, our data provide.two important re.ults: thyroid abnormalitie., aPL and incre.se. NK le.e.s are.more.pre.ale.t in wome. e.pe.ie.cing IVF failure. No e.ide.ce.was found for an association be.we.n inhe.ite. thrombophilia and Me.f and failure.to achie.e.pre.nancy afte. IVF.