Abstract: Objective: To investigate the clinical application of dalteparin sodium in patients with the repeated implantation failure caused by prethrombotic state． Methods: A retrospective analysis was performed on 125 patients with the repeated implantation failure in their 135 cycles of IVF-ET from January 2017 to December 2018． The patients were divided into the two groups: the observation group (58 cases, 62 cycles) was treated with routine luteal support therapy and dalteparin sodium during pregnancy; and the control group (67 cases, 73 cycles) was treated with only luteal support therapy. The pregnancy outcomes were compared between the two groups. Results: There were no significant differences in the age, body mass index, number of previous transplantation failures, number of embryo transplantation and basic FSH value between the two groups (P＞0.05). The clinical pregnancy rate and embryo implantation rate in the observation group were higher than those in the control group（37.1% vs. 21.6%, 36.5% vs. 23.4%）, and the abortion rate was lower (8.7% vs. 11.8%). The difference of embryo implantation rate was statistically significant (P＜0.05). During the treatment period in the observation group, there were 6 patients with a small amount of vaginal bleeding, and 2 patients with the mild transaminase increase. The level of transaminase returned to normal after heteropathy. Conclusions: Dalteparin sodium with a higher safety can significantly improve the outcome of re-thawed embryo transplantation in patients with prethrombotic status.

Key words: Prethrombotic state, Thrombosis, Recurrent implantation failure, Embryo Implantation, Dalteparin sodium