Microplastics in Human Ovarian Follicular Fluid and Female Fertility.

Microplastics and nanoplastics are increasingly reported in human biological matrices, raising concern about the exposure of the ovarian follicle during oocyte maturation. This narrative review evaluated evidence on plastic particles or polymer mass in human ovarian follicular fluid and their potential relevance to female fertility and assisted reproductive technology (ART). PubMed, including the Medical Literature Analysis and Retrieval System Online (MEDLINE); publisher records; reference lists; and citing articles were searched through July 28, 2026. Six full human observational studies and three preliminary reports were identified, demonstrating the limited size of the current evidence base. The full studies detected plastic-derived particles or polymer mass in human follicular fluid, although reported concentrations and polymer profiles differed substantially across analytical platforms. Several small studies associated higher polyethylene (PE) or polyvinyl chloride (PVC) burdens with lower fertilization rates, higher follicle-stimulating hormone (FSH) levels, or diminished ovarian reserve (DOR), while the largest case-control study reported the strongest association for polyamide 66 (PA66). These findings have not been independently replicated and remain observational. Cross-sectional designs, small and selected infertility-clinic populations, residual confounding, possible procedural contamination, nonequivalent measurement units, and the absence of standardized analytical methods preclude causal interpretation and quantitative comparison across studies. Animal and cell studies provide mechanistic plausibility but frequently use exposure conditions that may not represent human follicular exposure. Current evidence therefore supports the presence of plastic-derived material in the human follicular microenvironment but does not establish that microplastics cause infertility or that follicular-fluid testing has clinical utility. Prospective multicenter studies using standardized contamination controls, harmonized exposure measurements, and preregistered reproductive outcomes are required.