Background:Adequate thickness of the endometrium has been well recognized as a critical factor for embryo implantation. This was a prospective cohort study to investigate the benefits of platelet-rich plasma (PRP) for women with thin endometrium who received frozen embryo transfer (FET) program in a larger number of patients and explore the underlying mechanism.Methods:In this study, we investigated the effects of PRP in women with thin endometrium in FET program. 64 patients with thin endometrium (<7 mm) were recruited. PRP intrauterine infusion was given in PRP group during hormone replacement therapy (HRT) cycle in FET cycles.Results:After PRP infusion, the endometrium thickness in PRP group was 7.65 ± 0.22 mm, which was significantly thicker than that in control group (6.52 ± 0.31 mm) (P <.05). Furthermore, PRP group had lower cycle cancellation rate when compared to control group (19.05% vs. 41.18%, P <.01). The implantation rate and clinical pregnancy rate in PRP group were significantly higher than those in control group (27.94% vs 11.67%, P <.05; 44.12% vs 20%, P <.05, respectively). PRP blood contained 4 folds higher platelets and significantly greater amounts of growth factors including platelet-derived growth factor (PDGF)-AB, PDGF-BB, and transforming growth factor (TGF)-β than peripheral blood (P <.01).Conclusions:PRP plays a positive role in promoting endometrium proliferation, improving embryo implantation rate and clinical pregnancy rate for women with thin endometrium in FET cycles.