ИСТИНА

Objective: Leukaemia inhibitory factor (LIF) plays a central role in the control of implantation. LIF regulates multiple processes prior to and during implantation such as endometrial transformation into receptive state, embryo-endometrial interaction, stromal decidualization, tropfoblast invasion, blastocyst growth and development and uterine leukocyte infiltration. Abberant LIF production is linked to implantation failure. The aim (goal purpose) of this study was to determine whether LIF enriched transfer medium improves implantation and pregnancy rates in FET cycles. Design: prospective controlled study. Materials and methods: 1712 blastocysts with a grade of BB or higher were cryopreserved on day 5 or day 6 by vitrification technique. Warming was performed at least two hours prior the scheduled frozen embryo transfer. 798 blastocysts ( 737 cycles) were then cultured and transferred in global HP medium containing 10ng/ml LIF. The rest 914 blastocysts (812 cycles) cultured and transferred in global HP medium served as controls. For all transfers the volume of medium injected with the embryos did not exceed 20mkl. Clinical pregnancy was confirmed by the sonographic observation of a gestational sac. Implantation and clinical pregnancy rates were statistically analyzed using Chi- square test. Conclusion: Supplementing transfer medium with 10ng/ml LIF does not appear to improve implantation and pregnancy rates following frozen embryo transfer. Key Words: frozen embryo transfer, leukemia inhibitory factor, implantation. Study funding: By Russian Science Foundation, project 14-50-00029.