Ovarian stimulation leads to a severe implantation defect in mice.

The aim of the present study was to evaluate whether ovarian stimulation could induce embryo implantation dysfunction in mice and to explore the possible mechanisms involved. Ovarian stimulation was performed with intraperitoneal injections of 0, 2.5, 5.0, 7.5 and 10.0 IU pregnant mare serum gonadotrophin followed by the same dose of human chorionic gonadotrophin 48h later. A dose-dependent implantation defect in stimulated mice was demonstrated, which can be mainly explained by premature luteolysis and secondary endometrial changes induced by an imbalance in oestradiol and progesterone.