Microbial colonization of follicular fluid: Alterations in cytokine expression and adverse assisted reproduction technology outcomes

*This article is free to read on the publisher's website* BACKGROUND Previous studies have measured cytokines expressed within follicular fluid and compared the profiles with the aetiology of infertility and/or successful or unsuccessful assisted reproduction technology (ART) outcomes. METHODS In this study, 71 paired follicular fluid and vaginal secretions collected from ART patients were cultured to detect microorganisms and tested for the presence of cytokines. Patient specimens were selected for assay based on two criteria: whether the follicular fluid specimen was colonized (with microorganisms prior to oocyte retrieval) or contaminated by vaginal flora and; the aetiology of infertility. Patients included fertile women (with infertile male partners; n = 18), women with endometriosis (n = 16) or polycystic ovary syndrome (PCOS, n = 14), or couples with a history of genital tract infection (n = 9) or idiopathic infertility (n = 14). RESULTS Microorganisms and cytokines were detected within all tested specimens. Colonizing microorganisms in follicular fluid were associated with: decreased fertilization rates for fertile women (P = 0.005), women with endometriosis (P = 0.0002) or PCOS (P = 0.002) compared with women whose follicular fluid was contaminated at the time of oocyte retrieval and with decreased pregnancy rates for couples with idiopathic infertility (P = 0.001). A single cytokine was discriminatory for women with an idiopathic aetiology of infertility (follicular fluid interleukin (IL)-18). Unique cytokine profiles were also associated with successful fertilization (IL-1α, IL-1β, IL-18 and vascular endothelial growth factor). CONCLUSIONS Follicular fluid is not sterile. Microorganisms colonizing follicular fluid and the ensuing cytokine response could be a further as yet unrecognized cause and/or predictor of adverse ART outcomes and infertility.