The Correlation between Serum Levels of HLA-G and Recurrent Implantation Failure During Implantation Window in Women Undergoing In Vitro Fertilization

Background: Recurrent implantation failure (RIF) during artificial reproductive techniques (ARTs) remains a health problem. Many physiopathological pathways have been proposed for RIF, but the causes are not yet clear. Thus, the purpose of the current study was to evaluate the possible correlation between human leucocyte antigen-G (HLA-G) serum levels and recurrent implantation failure during the implantation window in women undergoing In vitro fertilization (IVF). Materials and Methods: In this prospective case-control study, 39 patients with RIF and 20 cases with successful implantation were enrolled as the control group. HLA-G serum levels were measured using the sandwich ELISA method in both groups. Results: HLA-G serum levels in the RIF group were significantly higher than in controls (0.085 ± 0.019 compared to 0.073 ± 0.005, p = 0.024). Furthermore, by grouping patients based on age and BMI, we found that in the cases with ages above 30 years and with BMI more than 25 (kg/m2), HLA-G serum levels in the RIF group were remarkably greater than controls (0.088 ± 0.019 compared to 0.072 ± 0.004, p = 0.002 and 0.083 ± 0.012 compared to 0.072 ± 0.003, p = 0.021, respectively). Conclusion: Serum levels of HLA-G increase in the RIF patients, especially in cases of patients above 30 years old and those with BMI ≥ 25, which remains significant after eliminating confounding variables. These results may indicate the involvement of physiopathological pathways of HLA-G in the increasing risk of RIF.