Association of the Systemic Immune-Inflammation Index with in Vitro Fertilization Treatment Outcomes in Women Undergoing GnRH Antagonist Protocol: a Cohort Study

What is the relationship between the systemic immune-inflammation index (SII) and IVF outcomes in women undergoing a gonadotrophin-releasing hormone (GnRH) antagonist protocol?This retrospective cohort study analysed clinical data and blood samples collected before oocyte retrieval from participants undergoing IVF with the GnRH antagonist protocol. Logistic regression and generalized additive models were used to examine the association between SII quartiles and continuous SII values and IVF outcomes.Higher SII values correlated negatively with biochemical pregnancy, clinical pregnancy, live birth and implantation rates, and positively with early pregnancy loss, independent of age, body mass index, anti-Müllerian hormone and stimulation parameters. The most significant adverse outcomes were observed in the highest SII quartile. A non-linear relationship was identified between log-transformed SII and IVF outcomes, with an inflection point at an SII of approximately 6.72, indicating a threshold effect.Elevated SII is associated with poorer IVF outcomes in women after the GnRH antagonist protocol, suggesting its potential as a predictive marker in IVF treatments. Further research is needed to confirm these findings and explore the underlying mechanisms.