The stage of embryo development does not significantly affect the success of frozen-thawed embryo transfer cycles, unlike fresh embryo transfer cycles. Blastocyst stage embryos have higher success rates than cleavage stage embryos in fresh transfers, but there is no difference in success rates between the two stages in frozen-thawed transfers. This means that in frozen-thawed cycles, both cleavage and blastocyst stage embryos have similar chances of resulting in a successful pregnancy and live birth.