Introduction: Low dose treatment with aspirin could result in endometrial improvement, decrease of abortion and consequently, an increase in uterine receptivity. Although many studies have been conducted on the effect of low dose of aspirin on the endometrium, there has not been any report on the effect of prescribing low dose of aspirin on the vascular density of endometrium. Thus, it was essential to conduct a study on this subject.
 Materials & methods: 15 female NMRI mice were used in this study. They were divided into three groups: control, sham and experimental groups. At first, in all groups, pseudo-pregnancy was induced and then the sham group received an injection of sterile water. The experimental group received low-dose of aspirin (7/5mg/kg) twice a day. Ovarian hormone levels were measured after 4.5 days of pseudo-pregnancy. Then the animals were sacrificed and the uterine horns were sampled for measurement of vascular density at implantation period. Finally, our results were statistically analyzed.
 Findings: Vascular density in the endometrium between two groups (control-experimental and sham-experimental) showed a statistically significant difference (P≤0/05).
 Discussion & Conclusion: Low-dose of aspirin seems to lead in changes of vascular density in the endometrium that may be effective on the embryo implantation.