Impact of ovarian stimulation on mid-luteal endometrial tissue and secretion markers of receptivity

The objective of this study was to investigate the effect of ovarian stimulation for IVF on endometrial secretion and tissue markers of receptivity in the mid-luteal phase. In 10 oocyte donors, endometrial secretions and biopsies were sampled 5 days after spontaneous ovulation and oocyte retrieval in consecutive cycles. Four subjects received progesterone in the luteal phase of the stimulated cycles. Mid-luteal endometrial maturation in the stimulated cycle was compared with the spontaneous cycle, by histological dating, Ki-67, oestrogen receptor (ER) and progesterone receptor (PR) expression, secretion levels of leukaemia inhibitory factor (LIF), glycodelin A (GdA) and progesterone, and protein profile. No significant differences in histological markers, expression of Ki-67, PR, ER, secretion protein profiles or concentrations of LIF, GdA, or progesterone were observed when comparing natural with stimulated cycles. Progesterone supplementation of stimulated cycles was associated with significantly lower Ki-67 (P = 0.03) and ER (P = 0.04) expression compared with the non-supplemented stimulated cycle. In this pilot study, ovarian stimulation was not demonstrated to alter the studied markers of endometrial maturation in the mid-luteal phase.