The effect of a high progesterone concentration before oocyte retrieval on the peri-implantation endometrium

In this single-centre, prospective cohort study, the effect of high progesterone level before oocyte retrieval on endometrial morphology and uterine natural killer cell (uKN) count in the peri-implantation period was investigated. A total of 106 women undergoing IVF treatment who did not proceed to fresh embryo transfer were included. Endometrial samples were obtained 7 days after HCG administration. Multiple regression analysis was used to identify factors affecting the results of histological staging and uNK cell count. Progesterone level on the day after HCG administration was the only significant variable associated with the results of histological staging (P = 0.004). Endometrial development in women with high progesterone level was significantly (P < 0.001) more advanced than that of women with normal progesterone; progesterone level on the day of HCG administration was the only significant variable associated with uNK cell count. The median (range) of uNK cell count of 9.6% (2.3-21.6%) in women with high progesterone was significantly (P < 0.001) higher than the median (range) of uNK cell count of 5.7% (1.4-18.7%) in women with normal progesterone. High progesterone level before oocyte retrieval was correlated with advancement in endometrial development as well as increased uNK cell count.