Abstract: Objective: To investigate the relationship between endometrial blood flow measured by Color Doppler on pre-implantation and in vitro fertilization and embryos transfer cycle（IVF-ET）. Methods: Data were obtained a total 70 women undergoing IVF-ET from May to November 2009. The endometrial thickness, blood flow status were detected by transvaginal ultrasonography on pre-implantation which include the third day after ovulation before IVF-ET cycles and the day of embryos transfer during IVF-ET cycles both. The patients were divided into three groups by the show of endometrial blood flow:Ⅰ, the number of the endometrial perforating blood flow ≤2 branch;Ⅱ, the number of the endometrial perforating blood flow 3~5 branch; Ⅲ, the number of the endometrial perforating blood flow≥6 branch. Results: In natural cycles, there is significant difference between the endometrial blood status of pregnancy groupand the non-pregancy group that（P ＜0.05）, and in stimulated cycles, there is no signtifically difference（P ＞0.05）. There is no significant difference between endometrial blood flow of the third day after natural ovulation and the day of ET as both were plentiful in pregnancy group（P >0.05）., but in non-pregnancy group the latter is more plentiful significantly than the former（P ＜0.01）. The parameters and endometrial thickness in pregnancy group were similar to non-pregnancy group in stimulated cycle and natrual cycle（P ＞0.05）. Conclusion: Richer of endometrial perforating blood flow in stimulated cycle have higher pregnancy rate, which can be as forecast level of endometrial receptivity. Stimulated cycle may change the endometrial receptivity, but do not have relevant evidence on the endometrial thickness and the parameters.

Key words: Endometrial blood flow, Stimulated cycle, Endometrial receptivity, IVF-ET