Abstract Study question Is the prostaglandin D2 (PGD2) associated with growing follicles and ovarian reserve of poor ovarian responders? Summary answer PGD2 is correlated with ovarian stimulation activity and follicle growth. Especially, poor ovarian responders show a significant decrease in the level of follicular fluid. What is known already Prostaglandins (PGs) are involved in the female reproductive process, mainly ovulation, fertilization, and implantation. Study design, size, duration We investigated the PGD2 level in the follicular fluid of poor ovarian responders. The collection of human follicular fluid was approved by the Institutional Research and Ethical Committees of CHA University (approval number: 1044308–201611-BR–027–04) from January to December 2019. Follicular fluid was collected from patients with normal ovarian response and patients with POR. Participants/materials, setting, methods We studied whether prostaglandin has related to POR in the clinical key factor by measuring human follicular fluid. Follicular fluid was collected from patients with normal ovarian response and patients with POR. The concentration of PGD2 in follicular fluid was determined with ELISA kits following the manufacturer’s protocol. Main results and the role of chance We analyzed the level of PGD2 in the follicular fluid of patients with normal ovarian response and patients with POR using an ELISA. The PGD2 concentration was significantly lower in the follicular fluid of patients with POR than in the follicular fluid of young and old patients with normal ovarian response. Limitations, reasons for caution This study has an identification of biomarker of the clinical samples as POR criteria patients. Therefore, further investigations aimed at specific recovery of low PGD2 metabolic activity in the CCs during control ovarian stimulation. Wider implications of the findings: Until now there is no specific biomarker of POR. AMH is just an ovary reserve marker for an indication of ovary function. PGD2 is one of the metabolites in steroid metabolism in the ovary. Therefore, we can find some cure through further study for improved PGD2 production to POR patients. Trial registration number none