OBEJECTIVETo compare the effectiveness of endometrial receptivity and pregnancy outcomes of four common immunomodulatory therapies for patients with thin endometrium.METHODThis systematic review and network meta-analysis using a literature search up to January 2024, to identify relevant trials comparing endometrial receptivity and pregnancy outcomes of human chorionic gonadotropin (hCG), platelet-rich plasma (PRP), infusion of granulocyte colony-stimulating factor (IG-CSF), and peripheral blood mononuclear cell (PBMC) for patients with thin endometrium. We used surface under the cumulative ranking (SUCRA) to ranked four common immunomodulatory therapies on endometrium thickness, implantation rate (IR), clinical pregnancy rate (CPR), and live birth rate (LBR). RoB2 and ROBINS-I were used to assess the certainty of evidence.RESULTSThe pooled results of 22 studies showed that hCG (mean difference [MD]: 3.05, 95% confidence interval [CI]: 1.46-4.64) and PRP (MD: 0.98, 95% CI: 0.20-1.76) significantly increase endometrium thickness. The hCG was the best among the IG-CSF (MD = -2.56, 95% CI = -4.30 to -0.82), PBMC (MD = -2.75, 95% CI = -5.49 to -0.01), and PRP (MD = -2.07, 95% CI = -3.84 to -0.30) in increasing endometrium thickness. However, IG-CSF and PRP significantly improved IR (IG-CSF: risk ratio (RR; IG-CSF: RR = 1.33, 95% CI = 1.06-1.67; PRP: RR = 1.63, 95% CI = 1.19-2.23), and LBR (IG-CSF: RR = 1.53, 95% CI = 1.16-2.02; PRP: RR = 1.59, 95% CI = 1.08-2.36).CONCLUSIONSAvailable evidence reveals that hCG and subcutaneous or intrauterine CSF (SG-CSF) may be the best treatment options for current thin endometrium patients. However, future high-quality and large-scale studies are necessary to validate our findings.