Effects of sequential and fixed-dose estradiol valerate administration on premature progesterone rise in frozen-thawed embryo transfer cycles

Aim: This study investigated the risk of premature progesterone (P4) rise in the fixed and sequential estradiol valerate (EV) administration for frozen embryo transfer (FET) cycles.Material and Method: In this cross-sectional case-control study, 1272 cycles of FET were analyzed retrospectively from computer records between January 2015 to August 2020. EV was administrated in 795 patients with a fixed dose and in 477 patients with a sequential dose. P4 values were measured on the day when the endometrial thickness reached 8 mm in the patients.Results: There were 795 patients in the fixed EV administration group with a mean age of 30.75±3.39 and 477 patients in the sequential EV administration with a mean age of 30.75±3.39. P4 of the sequential-dose group (1.05±0.31) was significantly higher than the fixed-dose group (1.01±0.33). The Pairwise Z-Tests found that the abort rate was significantly higher in the sequential-dose group (p=0.04).Conclusion: Our results showed a higher P4 and abortion rate in the sequential-dose group. These findings show that premature P4 rise can be considered a risk factor.