Low follicular fluid IL-6 levels in IVF patients are associated with increased likelihood of clinical pregnancy

PURPOSE: Relationships between follicular fluid levels of IL-6 with ovarian response and clinical pregnancy were evaluated in IVF-ET cycles. METHODS: Follicular fluid was collected from ovarian follicles ≥ 14 mm, pooled for each patient, and IL-6 levels were assessed using ELISA (n = 68). Relationships between IL-6 levels and IVF cycle parameters were assessed using nonparametric tests, and between IL-6 levels and clinical pregnancy using multivariable logistic regression analyses. RESULTS: Significant positive correlations were observed between IL-6 with age (p = 0.035), and IL-6 with estradiol on the day of hCG (p = 0.011). On adjusted analyses, IVF cycles in patients with IL-6 levels <4.0 pg/ml (median value for the group) demonstrated an almost 4-fold increase in likelihood for clinical pregnancy (p = 0.045). CONCLUSIONS: Lower follicular fluid IL-6 levels in IVF patients are associated with increased likelihood of clinical pregnancy. We hypothesize that endometrial receptivity is a likely target for any deleterious influences of elevated IL-6 levels.