Maternal characteristics
A total of 23726 FET cycles were included in this study, of which, 763
cycles were single cleavage-stage embryo transfers (C-1 group), 13004
were double cleavage-stage embryo transfers (C-2 group), 7913 were
single blastocyst-stage embryo transfers (B-1 group), and 2046 were
double blastocyst-stage embryo transfers (B-2 group). Maternal
characteristics for all FET cycles and for each group are summarized in
Table 1. Maternal characteristics among the four groups were
statistically different for maternal age, BMI, infertility type, cause
of infertility, duration of infertility, type of fertilization in the
current cycle, and previous ART cycles (P<0.05). Results of
pairwise comparisons of maternal characteristics between the groups are
shown in Table S1.