Blastocyst-stage embryos provide better frozen-thawed embryo transfer outcomes for young patients with previous fresh embryo transfer failure.

Older patients or patients with a reduced ovarian response have a low number of embryos, which limits the opportunity for embryo selection. However, for young patients undergoing frozen-thawed embryo transfer (ET), it remains unclear whether embryo stage affects pregnancy outcomes. In the present study, a total of 2952 patients undergoing their first frozen-thawed ET were divided into two groups: patients who had experienced one failed fresh ET (Group A) and patients who had not received fresh ET because of the high risk of ovarian hyperstimulation syndrome (OHSS) (Group B). Our results show that Group B patients had a significantly higher clinical pregnancy rate (CPR) and live birth rate (LBR) than Group A patients. However, Group A patients who underwent blastocyst-stage frozen-thawed ET had a significantly higher CPR and LBR and a lower ectopic pregnancy rate (ePR) than did those who underwent cleavage-stage frozen-thawed ET. In Group B, CPR, ePR, LBR and spontaneous abortion rate (sAR) were similar with blastocyst-stage and cleavage-stage frozen-thawed ET. These results suggest that blastocyst-stage frozen-thawed ET is more appropriate for young patients who had previously undergone one failed fresh ET cycle.