The Effect Of Endometrial Mechanical Stimulation On Pregnancy Outcome During Frozen-thawed Embryo Transfer Cycle

Objective: To investigate the effects of endometrial scratch and different methods of operation,the time interval between scratch and embryo transfer day and the timing of operation on pregnancy outcome and endometrial receptivity during freeze-thaw embryo transfer cycle.Methods: A retrospective collection of frozen-thawed embryo transfer(FET)cycles for patients with no history of implantation failure from January 2016 to December 2018 in the Reproductive Center of General Hospital of Tianjin Medical University.Part 1:They were divided into Non-scratch group(n=159)and Scratch group(n=539)according to whether endometrial scratch had been performed,to explore the effect of endometrial scratch on pregnancy outcome.Part 2:The transfer cycles of endometrial scratch were divided into Curettage group(n=419),Hysteroscopy group(n=70),Cell collector group(n=50),and control group(n=159),to explore the best method of endometrial curettage.Part 3: In order to explore the suitable transfer time after endometrial scratch,the transfer cycle of curettage operation was divided into Group B(n=104;time interval between endometrial scratch and embryo transfer <3 months),Group C(n=205;time interval of 3-6 months)and Group D(n=110;time interval of 3-6 months),Group A(n = 159)was not scratched.Part 4: In order to explore the optimal operation time of endometrial scratch,the curettage cycle was divided into Menstrual scratch group(n=161)and Luteal scratch group(n=258).The embryo implantation,clinical pregnancy,multiple pregnancy,miscarrage,ectopic pregnancy rates and endometrial receptivity index under ultrasound were compared.Result:1.The embryo implantation and clinical pregnancy rates of Scratch group were improved compared with the Non-scratch group,but the difference was not statistically significant(p > 0.05).There was no significant difference in multiple pregnancy,miscarrage and ectopic pregnancy rates between the two groups(p > 0.05).Compared with the Non-scratch group,the endometrial blood flow of type II and III increased,while that of type I decreased(p < 0.01).However,there were no significant difference in endometrial thickness,morphology and peristalsis between the two groups(p > 0.05).2.The embryo implantation rate in Curettage group was significantly higher than that in Non-scratch group(40.11% vs 30.94%,p=0.04).The clinical pregnancy rate also increased and the difference tended to be statistically significant(p=0.07).There were no significant difference in multiple pregnancy,miscarrage and ectopic pregnancy rates(p > 0.05).The embryo implantation and clinical pregnancy rates in Hysteroscopy group were higher than those in Non-scratch group,but there was no significant difference(p > 0.05).There were no significant difference in multiple pregnancy,miscarrage and ectopic pregnancy rates(p > 0.05).There were no significant differences in embryo implantation,clinical pregnancy,multiple pregnancy,miscarrage and ectopic pregnancy rates between the Cell collector group and the Non-scratch group(p > 0.05).The blood flow of type II endometrium in Curettage group was significantly higher than that in Non-scratch group,and the type I was significantly decreased(p < 0.01).There were no significant difference in endometrial thickness,endometrial morphology and peristalsis(p > 0.05).There were no significant difference in endometrial thickness,endometrial morphology,endometrial blood flow and endometrial peristalsis between Hysteroscopy group,Cell collector group and Non-scratch group,but there was still an increase in type II endometrial blood flow and a decrease in type I in Hysteroscopy group and Cell collector group.3.Pregnancy outcome analysis of group A,B,C and D: The embryo implantation rate of Group B and C was significantly higher than that of Group A(p < 0.05).The embryo implantation rate of Group D increased,but there was no significant difference compared with Group A(p > 0.05).The clinical pregnancy rate in Group B was higher than that in Group A,the difference tends to be statistically significant(p=0.08).The clinical pregnancy rate of Group C and Group D was higher than that of Group A,but there was no significant difference compared with Group A(p > 0.05).There were no significant differences in multiple pregnancy,miscarrage and ectopic pregnancy rates between Group B,C and D and Group A(p > 0.05).Assessment of endometrial receptivity by ultrasonography in Groups A,B,C and D: Compared with Group A,type II blood flow in Group B and C increased significantly,type I blood flow decreased significantly(p < 0.01).Compared with Group A,type II blood flow increased and type I blood flow decreased in Group D,but there was no significant difference(p > 0.05).There was no significant difference in endometrial thickness,morphology and peristalsis between Group B,C,D and Group A on transfer day(p > 0.05).4.There were no significant differences in embryo implantation,clinical pregnancy,multiple pregnancy,miscarrage and ectopic pregnancy rates between Menstrual scratch group and Luteal scratch group(p > 0.05).There was no significant difference in endometrial thickness,endometrial morphology,endometrial blood flow and endometrial peristalsis between the Menstrual scratch group and Luteal scratch group(p > 0.05).5.Pregnancy outcomes of different endometrial blood flow types on the day of transfer: The embryo implantation rates in Type II and III blood flow groups were significantly higher than those in Ttype I blood flow group(p < 0.05).The clinical pregnancy rate in Type II and III blood flow groups was higher than that in Type I blood flow group(p > 0.05).There was no significant difference in miscarrage and ectopic pregnancy rates between Type II blood flow group and Type I group(p > 0.05).Conclusion: 1.Curettage of endometrium can improve the pregnancy outcome of FET cycle in subfertile women without implantation failure.It was suggested that the implantation rate could significantly increase when the time interval between endometrial scratch and embryo transfer is shorter than 6 months,and the clinical pregnancy rate also tends to increase.2.Endometrial scratch may improve pregnancy outcomes by increasing endometrial blood flow,and this effectiveness is weakened over time.3.There was no significant difference in the pregnancy outcome of scratch of endometrium during menstruation or corpus luteum.