Objective: There is an increasing evidence supporting the role of a regulated cytokine network in the ovulatory process. In humans, it has been shown that follicular fluid (FF) exerts chemotactic activity toward granulocytes and that activity is related to the outcome of in vitro fertilization (IVF) treatment. Reactive oxygen species (ROS) in FF have been shown to be a potential marker of pregnancy in IVF patients. The objective of this study was to investigate the role of FF cytokines and ROS in the periovulatory FF during IVF cycles.Design: A prospective studyMaterials/Methods: Follicular fluid from 112 women was obtained while they underwent oocyte retrieval for IVF. We measured the concentrations of 5 cytokines (IL-1, IL-2, IL-12, IL-13, and TNF-) and ROS in FF and compared the levels among women who became pregnant and those who did not. Thirty-one endometriosis patients, 15 with idiopathic infertility, 21 with tubal-factor infertility, 15 with ovarian-factor infertility, and 30 patients with male-factor infertility were included. Tabled 1VariablePregnant Cycles (n = 52)Non-pregnant Cycles (n = 60)P-valuesAge (years)33.61 ± 3.5534.17 ± 4.25NSDuration of stimulation (days)9.56 ± 1.539.55 ± 1.79NSNo. FSH ampouls used35.30 ± 11.4138.02 ± 11.74NSNo. of oocytes retrieved12.27 ± 6.8811.87 ± 7.11NSFertilization rate0.66 ± 0.210.64 ± 0.22NSNo. of frozen embryos (2 pn)1.72 ± 3.730.97 ± 0.32NSNo. of frozen embryos (blastocysts)1.23 ± 1.940.70 ± 1.53NSROS (cpm)22.83 ± 26.676.74 ± 8.570.0400IL-1B (pg/mL)0.66 ± 0.900.50 ± 0.65NSIL-12 (pg/mL)3.87 ± 10.7024.45 ± 20.150.002NS - not significant Open table in a new tab Results: Interleukin-2, IL-13 and TNF-were not detected in the periovulatory FF in all patients. Fifty-two patients achieved pregnancy where 60 did not. Both pregnant and non-pregnant patients were comparable regarding age, parity, ovarian stimulation parameters, fertilization rates, and embryo freezing rates (table). Levels of FF IL-1 were not significantly different between pregnant and non-pregnant cycles. Levels of FF ROS were significantly higher in pregnant compared to non-pregnant cycles (p = 0.04). Levels of FF IL-12 were significantly lower in pregnant compared to non-pregnant cycles (p = 0.0002).Conclusions: Higher levels of IL-12 and lower levels of ROS in the periovulatory FF appear to be associated with a negative outcome in IVF treatment. Both IL-12 and ROS are powerful biological markers that appear to affect folliculogenesis, oocyte quality, and/or implantation.Supported by: None. Objective: There is an increasing evidence supporting the role of a regulated cytokine network in the ovulatory process. In humans, it has been shown that follicular fluid (FF) exerts chemotactic activity toward granulocytes and that activity is related to the outcome of in vitro fertilization (IVF) treatment. Reactive oxygen species (ROS) in FF have been shown to be a potential marker of pregnancy in IVF patients. The objective of this study was to investigate the role of FF cytokines and ROS in the periovulatory FF during IVF cycles. Design: A prospective study Materials/Methods: Follicular fluid from 112 women was obtained while they underwent oocyte retrieval for IVF. We measured the concentrations of 5 cytokines (IL-1, IL-2, IL-12, IL-13, and TNF-) and ROS in FF and compared the levels among women who became pregnant and those who did not. Thirty-one endometriosis patients, 15 with idiopathic infertility, 21 with tubal-factor infertility, 15 with ovarian-factor infertility, and 30 patients with male-factor infertility were included. Tabled 1VariablePregnant Cycles (n = 52)Non-pregnant Cycles (n = 60)P-valuesAge (years)33.61 ± 3.5534.17 ± 4.25NSDuration of stimulation (days)9.56 ± 1.539.55 ± 1.79NSNo. FSH ampouls used35.30 ± 11.4138.02 ± 11.74NSNo. of oocytes retrieved12.27 ± 6.8811.87 ± 7.11NSFertilization rate0.66 ± 0.210.64 ± 0.22NSNo. of frozen embryos (2 pn)1.72 ± 3.730.97 ± 0.32NSNo. of frozen embryos (blastocysts)1.23 ± 1.940.70 ± 1.53NSROS (cpm)22.83 ± 26.676.74 ± 8.570.0400IL-1B (pg/mL)0.66 ± 0.900.50 ± 0.65NSIL-12 (pg/mL)3.87 ± 10.7024.45 ± 20.150.002NS - not significant Open table in a new tab NS - not significant Results: Interleukin-2, IL-13 and TNF-were not detected in the periovulatory FF in all patients. Fifty-two patients achieved pregnancy where 60 did not. Both pregnant and non-pregnant patients were comparable regarding age, parity, ovarian stimulation parameters, fertilization rates, and embryo freezing rates (table). Levels of FF IL-1 were not significantly different between pregnant and non-pregnant cycles. Levels of FF ROS were significantly higher in pregnant compared to non-pregnant cycles (p = 0.04). Levels of FF IL-12 were significantly lower in pregnant compared to non-pregnant cycles (p = 0.0002). Conclusions: Higher levels of IL-12 and lower levels of ROS in the periovulatory FF appear to be associated with a negative outcome in IVF treatment. Both IL-12 and ROS are powerful biological markers that appear to affect folliculogenesis, oocyte quality, and/or implantation. Supported by: None.