Should zygote intrafallopian transfer be offered to all patients with unexplained repeated in-vitro fertilization cycle failures?

Background: One of the suggest strategy for patients with repeated implantation failure (RIF) is zygote intrafallopian transfer (ZIFT). However, no data exist regarding to the issue of when and under which circumstances should ZIFT be offered to patients with RIF? We therefore aimed to examine whether repeated implantation failure (RIF) patients characteristics or their previous controlled ovarian hyperstimulation (COH) variables may differentiate between those who will conceive following a ZIFT cycle and those who will not. Methods. Forty seven consecutive women admitted to our IVF unit during a 7 year period, who underwent ZIFT for RIF, were included. Ovarian stimulation characteristics, number of oocytes retrieved and number and quality of zygotes/embryos transferred were assessed and compared between the ZIFT cycle and the previous IVF/ICSI cycle and between those who conceived following the ZIFT cycle and those who did not. Results: Twelve clinical pregnancies (clinical pregnancy rate- 25.5%) were recorded following the ZIFT cycle. Those who benefit from ZIFT were young patients (≤31 yrs), who underwent ≤6 cycle attempts, yielding over eight 2PN embryos with low (≤0.4) ratio of number of top-quality embryos to total 2PN embryos. Moreover, in those destined for a ZIFT cycle, only those with >7 2PN embryo should undergo a transfer of at least five 2PN embryos. Conclusions: Further large prospective studies are needed to identify the specific characteristics of RIF women who may benefit from ZIFT.