Natural killer cell subsets in endometrial fluid: a pilot study of their association with the endometrial cycle and reproductive parameters.

Purpose: To investigate if there are natural killer (NK) cells in endometrial fluid (EF) and their relationship with the endometrial cycle and reproductive parameters.

Methods: The population under study consisted of 43 women aged 18-40 undergoing infertility workup at our University Hospital in 2021-2022. The EF samples were obtained at the first visit to our unit, on occasion of the mock embryo transfer.