Abstract

To investigate how estrogen level on the endometrial transformation day for hormone replacement therapy-frozen-thawed embryo transfer cycle influences pregnancy outcome. A retrospective analysis was conducted on clinical data from 772 patients who underwent hormone replacement therapy-frozenthawed embryo transfer between January 2016 and January 2020 in the Reproductive Medicine Center, Maternal and Child Health Hospital of Shaoguan City. The patients were divided into 5 groups according to their estradiol level on the endometrial transformation day as follows: Group A (estradiol<150 pg/ ml, 126 cycles). Group B (150≤estradiol<300 pg/ml, 318 cycles); Group C (300≤estradiol<450 pg/ml, 154 cycles); Group D (450≤estradiol<900 pg/ml, 115 cycles); Group E (estradiol>900 pg/ml, 59 cycles). There were no statistically significant differences in the general conditions among the 5 groups (p>0.05). Further comparative analysis on pregnancy outcomes among the 5 groups showed that there were no statistically significant differences in clinical pregnancy rate, embryo implantation rate and ectopic pregnancy rate among the 5 groups (p>0.05), but the first trimester abortion rate of Group E (30.3 %) was higher than that of Groups B to D (13.0 %, 11.4 %, 9.0 %) obviously and the difference was statistically significant (p<0.05). A further comparison of live birth rate among the 5 groups showed that the rates in Group A (35.7 %) and Group E (35.6 %) were lower than in Groups B to D (45.3 %, 46.8 %, 44.3 %), but there was no statistically significant difference (p>0.05). During the hormone replacement therapy-frozen-thawed embryo transfer cycle, high levels of estrogen may be associated with first trimester abortion. Moreover, when the estrogen level on the endometrial transformation day was within the range of 150-900 pg/ml, the live birth rate was relatively high.