The aim of this study was to explore the potential relationship between different KIR genotypes and reproductive outcomes (including chronic endometritis, abortion rate, endometrial quality (described by symptoms associated with endometrial pathology and hysteroscopic modifications), endometrial receptivity (quantified through LIF cytokine level) and the regulatory abilities of the NK cells (quantified through IL-1β and TNF-α cytokine levels). This evidence concerns the gene IL1B and chronic endometritis.