Effect Of Estrogen Starting Time On The Outcome Of Frozen-Thawed Embryo Transfer In Hormone Replacement Treatment After GnRHa Down Regulation

Objective:The objective of this study was to find out the best time to applying estrogen when preparing endometrium in frozen-thawed embryo transfer(FET)cycles.PART 1Methods:A retrospective study was done enrolling 827 cycles of patients with endometrium prepared by hormone replacement treatment after Gn RHa down regulation in Reproductive Center of Nanjing Maternal and Child Health Hospital from January 2017 to July 2018.The patients were divided into 4 groups by interquartile range according to the serum estradiol(E2)level on the day of estrogen administration.Group A:E2 ≤18 pg/m L;Group B:18 < E2 ≤ 23 pg/m L;Group C:23 < E2 < 32 pg/m L;Group D:E2 > 32 pg/m L.The baseline characteristics,clinical indicators after downregulation and pregnancy outcome of each group were compared among the four groups.Results:There were no statistically significant differences in baseline characteristics among groups A,B,C,D(P>0.05),except the number of good-quality embryos transferred(P<0.01).There was no significant difference in clinical pregnancy rate,early miscarriage rate,and live birth rate as well(P>0.05).The results remained the same after adjusting for the number of high-quality embryos transplanted,age,BMI and other potential factors.PART 2Methods:The fluctuation of E2 was further recorded in the 827 cycles included in the first part of this study,a total of 436 cycles appeared a clear trend of upward or downward.According to the trend of serum E2 level before the start of estrogen,it was divided into two groups.E2 showed an upward trend before estrogen use in the upward group and a downward trend before estrogen use in the downward group.Then compare the baseline characteristics,clinical indicators after down regulation and pregnancy outcomes between two groups.Results:There was no statistically significant difference in baseline characteristics such as age,body mass index(BMI),years of infertility,and basic serum hormone between the upward group and downward group(P> 0.05).The average days of estrogen use and the amount of estrogen in upward group were lower than those in downward group,and the difference was statistically significant(P <0.05).The early miscarriage rate in upward group was lower than that in downward group,the difference was statistically significant(P <0.05).Conclusions:In the artificial cycle with previous down-regulation of the pituitary,it was better to start the use of exogenous estrogen when the serum E2 level showed an upward trend,which can shorten the use time of exogenous estrogen,save the amount of medicine,and help avoid early miscarriage.