Introduction: In this study human follicular fluid has been used as an enzyme- rich solution to prevent embryo implantation in mice which resulted in reduction of pregnancy rate. Materials & Methods: 2-6 month NIH female mice were used to study the effect of interauterine follicular fluid on the fertility rate. 226 plugged female mice were caged in three groups: control, placebo, and experimental groups. Filterated active human follicular fluid was injected on the 4th day of pregnancy transvaginally to the uterine horns of the experimental group. In the pucebo group Ham's F10 medium was injected on the a day and in the same method, and the control group got no injection. After delivery, the number of embryos per mice and pregnancy rate were evaluated. Results: The statistical analysis indicated that: 1) There was a signitificant difference (P<0.05) between the experimental and the other groups, regarding the embryos per mice. ii) In the pergnancy rate, a significant difference (P<0.001) was observed between the experimental and the other groups. No significant difference was observed between the control and the placebo groups in any case. Cunclusion: The transvaginal injection of human fresh follicular flouid in mice at the expected time of implantation may interecept pregnancy and reduce both embryos per mice and the rate of pregnancy. This effect of the pollicular fluid could be due to its negative effects on the endometrial rey in the time of implantation window or per-embryo development or both. The exact mechanism of these and the effective fraction(s) of the folicular fluid in pregnancy interception need mors studies.