Clinical Study Of Influencing Factors And Strategies In Frozen-Thawed Embryo Transfer Cycles

Part Ⅰ Factors Affecting the Clinical outcomes of Frozen Embryo Transfer Cycles in Women Recieving FET Treatment[Objective]To explore the relationship between different factors and the clinical outcomes of frozen-thawed embryo transfer（FET）in patients,and to provide effective guidance for improving the FET clinical outcomes.[Materials&Methods]This retrospective analysis included 235 infertile women who underwent FET treatment in the Reproductive Center of Nanfang Hospital.They previously had a successful pregnancy outcome utilizing IVF-ET and had at least two good-quality cryopreserved cleavage-stage embryos remained from the same oocyte retrieval cycle.The main variables being examined are maternal transplant age,the number of eight-celled embryos transferred,endometrial thickness on the day of transplantation,previous delivery mode,fertilization method,endometrial preparation protocol,timing of transplantation,and embryo storage time.Chi-square analysis and binary regression analysis were used to determine the influence on different factors and FET outcomes including implantation rate,clinical pregnancy rate,live birth rate,and miscarriage rate.[Results]（1）For women who have a high-quality cleavage embryo after FET,the results show that the implantation rate and live birth rate were significantly higher in patients with endometrial thickness≥8mm on the day of transplantation compared to those with endometrial thickness<8mm（P<0.05）.Furthermore,the implantation rate,clinical pregnancy rate,and live birth rate were significantly lower in the cesarean section group compared to the vaginal delivery group（P<0.05）.Additionally,the implantation rate was significantly higher in the group receiving two eight-cell embryos compared to the group receiving non-eight-cell embryos（P<0.05）.（2）Logistic regression analysis showed that two eight-cell embryos and vaginal delivery were protective factors of the FET outcomes for infertility patients（OR>1,P<0.05）.（3）Among patients with endometrial thickness<8mm on the day of transplantation,the implantation rate,clinical pregnancy rate and live birth rate in the vaginal delivery group were significantly higher than those in the cesarean section group（P<0.05）,while there were no significant differences in clinical outcomes among the patients with endometrial thickness≥8mm on the day of transplantation（P>0.05）.（4）The maternal transplant age,fertilization method,timing of transplantation,and embryo storage time were not found to be correlated with the FET clinical outcome（P>0.05）.[Conclusions]（1）The number of eight-cell embryos and the mode of delivery in frozen-thawed embryo transfer were found to be significant factors affecting the clinical outcomes in infertile patients undergoing FET treatment.（2）Patients who underwent cesarean section during their last pregnancy with an endometrial thickness of<8mm on the day of transplantation were shown to have a negative impact on the FET clinical outcome.Part Ⅱ Optimizing the number of embryos transplanted during FET to optimize pregnancy outcome[Objective]To explore the proper cleavage embryo transfer protocols in frozen-thawed embryo transfer cycles for patients of different oocytes retrieval ages.[Materials&Methods]A retrospective study was conducted on 2265 patients who received FET treatment at Reproductive Medicine Center,Nanfang Hospital,Southern Medical University from January 2018 to May 2020.According to the different grades and number of transplanted embryos,patients were divided into 5 groups:a single non-high-quality embryo group（A₀ group,n=45 cases）,single highest-quality group（A₁ group,n=252 cases）,double non-high-quality embryos group（B0 group,n=112 cases）,one high-quality and one non-high-quality embryos group（B₁ group,n=360 cases）and double high-quality embryos group（B₂ group,n=1496 cases）.The clinical outcomes of each group were analyzed.Patients in Group A₁,B₁ and B₂ were assigned into subgroups based on patients’ different oocyte retrieval ages and the pregnancy outcomes were compared.[Results]（1）The live birth rates in Group A₀,A₁,B₂,B₁ and B0 were 13.33%,33.33%,48.06%,33.33%and 25.89%（P<0.001）,respectively,while the multiple pregnancy rates were 0%,0%,41.29%,23.72%and 24.39%（P<0.001）,respectively.（2）Stratified analysis was conducted in Group A₁,B₂ and B₁ based on patients’ different occytes retrievel ages.Among patients’ oocytes retrieval ages<30 years,the live birth rate of patients in Group A₁,B₂ and B₁ were 46.67%,61.94%and 50.00%（P<0.001）,respectively,and the multiple pregnancy rate were 0%,44.64%and 18.18%（P<0.001）,respectively.（3）Among patients’ oocytes retrieval ages between 30 and 34 years,the live birth rates of Group A₁,B₂ and B₁ were 40.20%,61.35%and 42.86%（P<0.001）,respectively,and multiple pregnancy rates were 0%,44.51%and 32.61%（P<0.001）,respectively（4）Among patients’ oocytes retrieval ages between 35 and 38 years,the live birth rates of Group A₁,B₂ and B₁ were 15.79%,46.28%and 35.56%（P<0.001）,respectively,and multiple pregnancy rates were 0%,38.30%and 19.51%（P<0.001）,respectively.（5）Among patients’ oocyte retrieval ages between 39 and 40 years,the live birth rates of Group A₁,B₂ and B₁ were 10.00%,28.29%and 26.47%（P>0.05）,respectively,and the multiple pregnancy rates were 0%,25.00%and 31.58%（P>0.05）,respectively.（6）Among patients’ oocytes retrieval>40 years old,the live birth rates of Group A₁,B₂ and B₁ were 3.70%,11.48%and 12.64%（P>0.05）,respectively,and the multiple pregnancy rates were 0%,14.00%and 11.76%（P>0.05）,respectively.[Conclusions]（1）For the first or second transfer cycle in patients of oocyte retrieval ages<35 years,single cleavage embryo transfer is a desirable option.（2）For patients of oocyte retrieval ages between 35-38 years,as the rate of multiple pregnancy is still high,it is recommended to transfer a single high-quality cleavage embryo in cleavage embryo transfer.（3）For patients of oocytes retrieval ages>38 years,the embryo transfer protocol should be determined according to the patients’ embryo quality,previous cycles and other factors.