Effect of endometriosis on early embryonic development in the rabbit

The reasons for sub-fertility in patients with mild endometriosis remain unclear. Peritoneal fluid constituents may alter tubal transport and embryonic cleavage, with subsequent implantation disturbances. We used an animal model to study the influence of endometrial implants on early embryonic development. In 25 rabbits, endometrium from the right uterine horn was transplanted onto the peritoneum (Experimental group = Group E). In 25 rabbits, fat was transplanted (control group = group C). After a recovery period of 12 weeks the does were mated, and killed 24 h later. In the experimental group the implants had changed into cysts of 5-15 mm in diameter. Histological examination revealed endometrial glands and stroma in every specimen. Periadnexal adhesions did not develop in any animal. No marked differences were found between Groups E and C in embryonic cleavage stage, 24 h after mating. Additional culturing of the embryos for 48 h in a suitable culture medium revealed normal further development of the embryos. Bearing in mind the restrictions of extrapolating a rabbit model to the human, it is suggested that the decreased fecundity in mild endometriosis is not caused by altered early embryonic cleavage rate. The results of this study offer indirect evidence for implantation disturbances as a cause of endometriosis-associated sub-fertility.