Results
The demographic characteristics of the patients/cycles included in the
study are presented in Table I. The variables were compared using
Student’s t-test, and despite the infertility time, the number of total
and metaphase II oocytes collected had statistically significant
differences, the groups were clinically comparable.
Clinical outcomes
For the first FET, we compared the clinical outcomes of the eDET and
eSET groups (Table II). The eDET group had a significantly higher
multiple PR and a significantly lower implantation rate, as expected,
and the ongoing PRs were similar between the two groups. Conversely,
when a second SET was performed in patients who did not become pregnant
in the first frozen-thawed eSET (eSET + SET, n = 60), 16 ongoing
pregnancies (26.7%) were achieved in this group. Thus, the estimated
cumulative ongoing PRs of the
eSET
+ SET subgroup were calculated according to the previously described
formula, and became significantly higher from those of the eDET group
(Figure 2).
The multiple linear regression
model evaluated the association of transferring two embryos in two
sequential transfers (eSET + SET), compared with the eDET protocol, with
the chance of embryo implantation. The model was adjusted for
confounders such as the women’s age and the number of cryopreserved
embryos. We obtained a statistically significant model, in which the
transfer of two embryos in two sequential transfers (eSET + SET) led to
a significantly higher chance of implantation than did the transfer of
two embryos together (eDET) in freeze-only cycles (coefficient: 0.142, p
< 0.001), adjusted for women’s age and number of cryopreserved
embryos available (Table III).