DOES PROLONGED ESTRACE ADMINISTRATION EFFECT ON PREGNANCY OUTCOME IN PROGRAMMED FROZEN EMBRYO TRANSFER CYCLE?

Abstract

To determine whether women in frozen-thawed embryo transfer (FET) cycles, who continued prolonged estrogen administration beyond the standard 12 days due to a thin endometrial stripe exhibited lower pregnancy rates. We retrospectively analyzed the outcomes of 822 FET cycles from January 1, 2019 through March 1, 2021. Oocyte recipients or women with known intrauterine adhesions were excluded. Women received twelve days of 6 mg of oral 17 beta Estradiol (Estrace) after ovarian suppression was confirmed. If after twelve days of Estrace their endometrial stripe (ES) was equal to or less than 7 mm, then their estrogen regimen was continued until her ES was at least 7mm. Intramuscular progesterone 50mg intramuscularly was then administered and a single thawed blastocyst was transferred 132 hours later. Variables assessed included thickens of endometrium, pregnancy (serum hCG), clinical pregnancy, and implantation rate by fetal cardiac activity and pregnancy outcome. The Fisher’s Exact Test and t-test were used. A p value <0.05 was considered significant. Twenty three of 822 cycle were continued on their estrogen regimen to meet ES criteria for at least five days (range 5 to 14 days). No significant differences in age, prior failed FET cycles, and percentage of euploid blastocysts were noted between those women who did or did not requires at least five days more of exogenous estrogen. However, endometrial thickness was significantly thicker in regular FET group compared that of pushed FET cycle at day 12 (9.59 mm vs 6.16 mm, p<0.05). Furthermore, their thin endometrial thickness was significantly improved after prolonged Estrace (6.16 mm vs 7.49 mm, p<0.05). Among pushed FET cycles, five patients were pushed for 14 days and the endometrial thickness were improved from 4.78 mm to 7.08 mm (p=0.11). The pregnancy rate (positive serum hCG/total transfers), clinical pregnancy rates and implantation rate were not significantly different between regular and pushed FET cycles (73.2 %vs 75.0 %), (68.8 % vs 62.5 %), and (59.4 % vs 52.0 %), respectively. The pregnancy outcomes in two groups were similar by age group or PGT performed group. Additionally, chemical pregnancy loss or miscarriage rate did not differ between two groups (7 % vs 4%) and (7 % vs 4 %), respectively. Ongoing pregnancy/live birth rate was 60.9 % (14/23) for regular FET and 59.7 % (462/799) for pushed FET. Our findings suggest that continued exogenous estrogen administration successfully increased the endometrial thickness in all patients with a thin ES and did not adversely affect pregnancy outcome.