Materials and Methods: Adult male and female mice were used for the induction of pseudopregnancy. The mice were divided into two experimental and control groups. The Experimental group was further subdivided into two groups based on hormone injection: 1) antiprogesterone and 2) hyperstimulation + antiprogesterone. The control group did not get any hyperstimulation. All groups’ uteruses were collected after 4.5 days of pregnancy and were prepared for the assessment of the histological changes with light microscopy (LM) and Transition Electron Microscopy (TEM).

Results: The results showed that antiprogesterone injection decreases the height of microvilli and pinopods in the apical cell in comparison to the control group. Antiprogesterone injection increases the inflammatory cells in the lamina propria of endometrium. The histomorphometrical results indicated that endometrial luminal epithelium height in the hyperstimulation + antiprogesterone group was significantly different compared to the control group (P < 0.01).

Conclusion: These findings demonstrate that the use of mifepristone is associated with histological changes in the endometrium.