| Assisted reproductive technology（ART）has been in development for more than40 years.The ultimate goal of in vitro fertilization-embryo transfer（IVF-ET）is to obtain a full-term single-born healthy baby in the shortest possible time and at the lowest cost.It is well known that multiple pregnancy has become a common complication of ART,which can lead to adverse pregnancy and perinatal outcomes.Consequently,experts in reproductive medicine around the world have been working to minimize the rates of multiple pregnancy while maintaining acceptable levels of IVF pregnancy rates.Studies have found that single blastocyst transfer significantly reduces the multiple pregnancy rate and premature birth of patients,while maintaining a high clinical pregnancy rate[1-3].In recent years,major reproductive centers have vigorously carried out blastocyst culture,but blastocyst culture has some disadvantages,such as prolonging the time of in vitro culture,which may lead to the risk of no available embryo[4-6].Therefore,many patients can not accept full blastocyst culture.Most of the reproductive center on the basis of further adjusted the blastocyst culture strategy,all the remaining embryos were cultured on the premise of ensuring a small number of high-scoring cleavage embryos were transferred to patients.Not all embryos of patients can develop into high-quality blastocysts.When clinically encountering the situation of transplanting low-quality single blastocysts or double high-quality cleavage embryos,which is better to transplant needs further discussion.The outcome of different grades of cleavage embryos and blastocysts transplantation needs further discussion,so as to provide guidance for the formulation of clinical transplantation plan.ObjectivesTo explore the priority order of transferring low-quality blastocyst and high-quality cleavage embryos in the recovery frozen-thawed embryo transfer（FET）cycle of frozen embryos.Materials and Methods1.Study object:This study was a retrospective cohort study that retrieved FET cycles from May 2016 to September 2018 in the electronic database of the Reproductive Center of the Third Affiliated Hospital of Zhengzhou University.2.Inclusion criteria:Resuscitation cycle of 1 blastocyst or 2 cleavage embryos;the first or second transfer cycles.Exclusion criteria:Preimplantation genetic diagnosis and screening（PGD/PGS）;cycles with donor sperm or oocyte;repeated implantation failure;cycles involving incomplete medical records.3.Grouping:According to the number of embryos transferred and stage of embryo development,quality,embryos were divided into 5 groups:single-high-quality blastocyst group（group A）,single-non-high-quality blastocyst group（group B）,day 3（D3）double-high-quality embryo group（group C）,D3 high-quality plus non-high-quality embryo group（group D）and D3 double-non-high-quality embryo group（group E）.Each group was divided into two subgroups according to the age:younger than 35 years group and not younger than 35 years old group.4.Statistical analysis:SPSS21.0 software was used for statistical analysis of data in this study.Kolmogorov-smirnov test was used to test the normality of continuous variable data.The measurement data were described by meant±standard deviation（±s）,the sample mean was compared by one-way ANOVA,and the comparison between groups was LSD-t test.The count data is described by percentage,and the sample rate is compared by row x list chi-square test.The influencing factors of live birth were analyzed by binary Logistic regression.The statistical significance was set at P<0.05,P values were corrected by Brunden’s method for pairwise comparison between multiple sample rates.ResultsAfter strict screening by the above inclusion and exclusion criteria,a total of 4064FET cycles were included in this study,including 2208 cases in the<35 years old group and 1856 cases in the≥35 years old group.1.When patients were younger than 35 years old,the live birth rate of group A and group C was significantly higher than group B（P<0.006）.The clinical pregnancy rate of group A and group C was higher than group B,but the difference was not statistically significant（P>0.006）.Compared with group B,there were no significant difference in clinical pregnancy rate and live birth rate between group D and group E（P>0.006）.The miscarriage rate of group B was higher than other groups,while the difference was not statistically significant（P>0.006）.The premature birth rate of group C and D was significantly higher than that of group B（P<0.001）.2.When patients were not younger than 35 years old,the clinical pregnancy rate and live birth rate in group A～E decreased successively,but the differences of miscarriage rate and premature birth rate were not statistically significant compared with group B（P>0.006）.3.The implantation rates of double D3 embryos transfer groups（group C～E）at all ages were significantly lower than those of single blastocyst groups（group A and B）（P<0.001）,while the multiple pregnancy rates were significantly higher than those of single blastocyst groups（P<0.001）.4.Age,the type of embryos transferred and endometrial thickness on embryo transfer day were independent influencing factors for live birth,single live birth and twin live births.In addition,basal follicle stimulating hormone（b FSH）was an independent influencing factor for single live birth and body mass index（BMI）was an independent influencing factor for twin live births.Logistic regression analysis showed that,compared with group B,the effects of group A（OR=1.406,95%CI=1.153-1.715,P=0.001）,group E（OR=0.652,95%CI=0.500-0.849,P=0.001）on the live birth rate were significantly different,while the effects of group C（OR=1.207,95%CI=0.999-1.459,P=0.051）,group D（OR=1.046,95%CI=0.842-1.301,P=0.683）on the live birth rate were no significantly different;Compared with group B,the effects of group A[OR=1.433,95%CI（1.175-1.747）,P<0.001],group D[OR=0.759,95%CI（0.601-0.959）,P=0.021]and group E[OR=0.502,95%CI（0.378-0.666）,P<0.001]on live birth of single fetus were statistically significant,while the effects of group C[OR=0.833,95%CI（0.680-1.019）,P=0.075]on live birth of single fetus were no significantly different;For twin live births,the incidence of twin live births was significantly increased in the double embryo transfer group（group C～E）（P<0.001）.Conclusions1.The optimal transplantation sequence of frozen embryo transfer cycle was single-high-quality blastocyst,single-non-high-quality blastocyst,D3 double-high-quality embryo,D3 high-quality plus non-high-quality embryo and D3 double-non-high-quality embryo.2.Age,the type of embryos transferred and endometrial thickness on embryo transfer day were independent influencing factors for live birth,single live birth and twin live births. |
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