ABSTRACT
<p><b>OBJECTIVE</b>To check the expression of leukemia inhibitory factor (Lif) mRNA, and to study the impact of ovarian stimulation on the ability of embryo implantation in mice.</p><p><b>METHODS</b>Pregnancy models of mice were established. The relationship between the implantation of ovarian stimulated embryos and the expression of Lif mRNA in mice metrium was analyzed.</p><p><b>RESULTS</b>The group of recipients which the transfered embryos were from stimulated cycles had lower pregnancy and implantation rate compared with the group of recipients which the transfered embryos were from non-stimulated cycles (20.00%, 8.33% vs 55.00%, 35.00%). The Lif mRNA expression was similar in the groups of recipients which the transfered embryos were from stimulated and non-stimulated cycles, so was in the groups of recipients which had single or more than one baby, but higher in the group of pregnancy recipients than in the group of unpregnancy recipients.</p><p><b>CONCLUSION</b>Ovarian stimulation may reduce the ability of embryo implantation in mice. Lif mRNA expression is related to the implantation, but not parallel to the number of implantation.</p>