CD138 expression in the endometrium associates with endometrial timing and inflammatory status but not microbiota composition

The authors investigate the relationship between CD138 expression in the endometrium and the composition of the reproductive tract microbiota in women with a history of recurrent pregnancy loss. They find that while CD138+ cells in the endometrial stroma are cycle-dependent and associated with impaired endometrial timing, there is no significant correlation with the microbiota composition. This challenges the previously assumed link between CD138+ chronic endometritis and adverse reproductive outcomes, suggesting that CD138 levels are not influenced by bacterial factors and are more indicative of endometrial immaturity.