| Background: As an important supplement to in vitro fertilization-embryo transfer technology,freeze-thaw embryo transfer technology can effectively prevent complications related to fresh embryo transfer and improve the cumulative pregnancy rate,but the clinical pregnancy rate has always been hovering at 60%.Studies have shown that the success rate of FET is influenced by a number of factors,including patient and embryo implantation factors.Gn RHa is a gonadotropin-releasing hormone analogue that can promote the synchronous development of endometrium and embryo after hypophysis,which is conducive to pregnancy.Objective: The purpose of this research is to explore the influencing factors of FET cycle clinical outcome and the application value of HRT combined with gonadotropin-releasing hormone agonist pretreatment,so as to guide clinical medication.Methods:This is a retrospective study with 517 cycles who accepted in vitro fertilization（IVF）or intracytoplasmic sperm injection（ICSI）and frozen embryo transfer in the Reproductive Center of Taihe Hospital on the third or fifth day from January 2019 to December 2021.Then we analyze the related factors affecting the pregnancy rate of FET.According to whether gonadotropin-releasing hormone agonists were used or not,patients were divided into two groups: A（down-regulated group）and B（non-downregulated group）.The clinical pregnancy rate,biochemical pregnancy rate and ectopic pregnancy rate of FET cycles were compared between groups with advanced age,thin endometrial,RIF and AMH<2ng/ m L.Results: In the 517 FET cycles,334（64.6%）were successful pregnancies and 183（35.4%）were non-pregnancies.There were differences in average age,infertility years,AMH,induction cycle regimen,estrogen administration days,endometrial thickness,whether blastocyst was transplanted and or not the number of transplanted embryos between the two groups（P<0.05）.Logisttic analysis of the above indicators showed that age >40 years（OR=0.304,95%CI:0.124-0.743,P=0.09）,infertility years 2-6 years（OR=1.687,95%CI:1.074-2.65,P=0.023）,long-acting regimen（OR=3.260,95%CI :1.616-6.579,P=0.001）,antagonist regimen（OR=2.361,95%CI:1.252-4.455,P=0.008）,AMH（OR=1.839,95%CI:1.085-3.117,P= 0.024）and blastocyst transplantation（OR=2.431,95%CI:1.505-3.928,P= 0.000）were independent factors affecting pregnancy rate。According to the general situation of patients,elderly patients,thin endometrium,RIF and AMH<2ng/ml were screened and divided into two groups:group A（using Gn RHa）and group B（not using Gn RHa）.There was no statistical difference in general conditions（P>0.05）.It was found that estrogen administration days were shortened and endometrial thickness was increased（P<0.05）of patients with advanced age in group A,while clinical pregnancy rate（49.2%）,biochemical pregnancy rate（8.2%）increased,translocation pregnancy rate（0）decreased,but there was no statistical difference（P>0.05）.The estrogen administration days of patients with thin endometrium in group A were prolonged（P<0.05）,while clinical pregnancy rate（38.5%）and ectopic pregnancy rate（0）decreased,while the biochemical pregnancy rate（15.4%）increased,but there was no statistical difference（P>0.05）.The days of estrogen administration of RIF in group A were shortened and the intima thickness was increased（P<0.05）,The clinical pregnancy rate（55.7%）was decreased,while the biochemical pregnancy rate（9.8%）and ectopic pregnancy rate（5.9%）were increased,but there was no statistical difference（P>0.05）.Shorter estrogen administration days and intima thickening in patients with AMH<2ng/ml（P<0.05）,while the clinical pregnancy rate（38.9%）and biochemical pregnancy rate（14.8%）were increased,but there was no statistical difference（P>0.05）。Conclusion:.1.Blastocyst transplantation is beneficial to improve the pregnancy rate of FET;However,increasing the number of embryo transfer did not significantly increase the pregnancy rate,but increased the multiple embryo rate to a certain extent,so highquality single embryo transfer should be selected as far as possible when it is not necessary.2.In the case that embryos have been obtained,low AMH,advanced age（> 40years）and long infertility years can still adversely affect the pregnancy rate of FET,and FET should be used as early as possible;3.Endometrial thickness is not an absolute factor affecting pregnancy,but too thin is not conducive to embryo implantation.For TE patients,endometrial thickness should be increased as much as possible.However,if estrogen is used for too long,there is a risk of thrombotic diseases.Progesterone can be given to transform intima after the intima thickness reaches the standard.4.In FET,used routinely in patients with no special history of ordinary Gn RHa falling tone,not only increase their economic and mental burden,and no significant benefit,therefore is not recommended;5.For patients with advanced age,thin endometrium,RI and DOR of unknown causes,repeated use of routine endometrial preparation should be avoided.It is a good idea to try Gn RHa down-modulation preconditioning,which may achieve better clinical outcome. |
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