FET-E2-raw data.doc

Aim of the study To evaluate
the association between serum estradiol (E2) and pregnancy outcomes
of cleavage- or blastocyst-stage frozen embryo transfer (FET) cycles using
hormone replacement therapy.

Methods A
total of 776 FET cycles (669 couples) performed from January 2016 to December 2019
were included in the present retrospective cohort study. The impact of progesterone-initiation-day
serum E2 levels on the ongoing pregnancy/live birth (OP/LB) rates was
determined, and cleavage-stage embryo transfers and blastocyst-stage embryo transfers
were analyzed separately.

Results
Regarding cleavage-stage embryo transfer cycles, serum E2 levels on
progesterone initiation day were significantly lower in the OP/LB group than in
the non-OP/LB group (214.75 ± 173.47 vs. 253.20 ± 203.30 pg/ml; P = 0.023). In addition, there were
downward trends in implantation, clinical pregnancy and OP/LB rates with
increasing E2 levels. However, in blastocyst-stage embryo transfer
cycles, such trends were not observed, and there was no significant difference between
the OP/LB group and the non-OP/LB group. Logistic regression analysis revealed
that E2 levels on progesterone initiation day in cleavage-stage embryo transfer
cycles were independently associated with OP/LB (odds ratio = 1.000, 95%
confidence interval: 1.000-1.001, P = 0.008). The areas under the receiver
operating characteristic curve were 0.55 in cleavage-stage embryo transfer
cycles and 0.53 in blastocyst-stage embryo transfer cycles.

Conclusions The results
suggests that progesterone-initiation-day E2 levels should be
monitored during artificial cleavage-stage embryo transfer cycles. However, it
is not necessary to monitor serum E2 levels when transferring
blastocysts in artificial FET cycles.