To investigate the effect of intrauterine administration of autologous peripheral blood mononuclear cells (PBMCs) on pregnancy outcomes in patients with recurrent implantation failure (RIF) and the related mechanism.

Thirty-six RIF patients received intrauterine administration of PBMCs 24 h before the frozen-thawed embryo transfer, with observation of their pregnancy outcomes. Enzyme-linked immunosorbent assay (ELISA) was performed to detect the concentration of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in peripheral blood and cervical secretions before and after the treatment.

Following the PBMC intrauterine administration, this cohort of women with RIF received a higher clinical pregnancy rate (47.22%). The concentration of IL-6 and the radio of IL-6/TNF-α in the cervical secretions were significantly higher than before (P<0.05), while no change in TNF-α (P>0.05). No significant change was found in the concentrations of IL-6 and TNF-α in peripheral blood (P>0.05).

Intrauterine administration of autologous PBMCs increases the concentration of IL-6 and the radio of IL-6/TNF-α in the uterine cavity, and this method can effectively improve the clinical pregnancy rate in patients with RIF.

Recurrent implantation failure (RIF); Peripheral blood mononuclear cells (PBMCs); Intrauterine administration; Interleukin-6 (IL-6); Tumor necrosis factor-α(TNF-α)