Morphometric analysis of peri-implantation endometrium in patients having excessively high oestradiol concentrations after ovarian stimulation.

The present study investigated whether high oestradiol concentrations after ovarian stimulation in infertile women affect endometrial development around the time of implantation. The glandular and stromal components of the endometrium were assessed by morphometric criteria. Endometrial biopsies were taken on day 7 (+/-1) after the ovulating dose of human chorionic gonadotrophin in stimulation cycles and on day 7 after the LH surge in natural cycles. Women (n = 38) undergoing assisted reproduction treatment were evaluated: 12 women in natural cycles, 11 women in stimulation cycles with oestradiol <20,000 pmol/l and failed fertilization after oocyte collection (moderate responders) and 15 women with an oestradiol concentration of > or =20,000 pmol/l in stimulation cycles (high responders). High responders showed delayed glandular maturation and advanced stromal morphology, whereas moderate responders demonstrated synchronous development of glandular and stromal features. In natural cycles, the glands were in phase. The effect of excessively high oestradiol concentrations could be explained by quantitative evaluation of the endometrial biopsies as gland--stromal dyssynchrony, which indicates a deficient secretory transformation of the endometrium that represents a suboptimal endometrial environment for implantation. This substantiates our previous clinical observation of significantly lower pregnancy rates in IVF cycles of women with high oestradiol concentrations (> or =20,000 pmol/l).