Effects of waiting time between failed fresh cycle embryo transfer and the next frozen embryo transfer on pregnancy outcomes in assisted reproductive technology.

Objective: To explore how waiting time after failed fresh cycle embryo transfer affects the pregnancy outcomes of the next frozen embryo transfer (FET). Methods: A retrospective analysis was carried out on the data of women who had received at least one FET after a failed fresh embryo transfer between January 2013 to December 2019. The women were grouped based on the "time" of the first FET, referring to the period between a failed fresh embryo transfer and the beginning of the next cycle of FET. This time is divided into two classes: immediate (<90 days after the failed fresh embryo transfer) and delayed (≥90 days after failed fresh embryo transfer). The following parameters were investigated: clinical pregnancy rate; biochemical pregnancy rate; ectopic pregnancy rate; and non‐pregnancy rate. Results: A total of 293 cases of fresh embryo transfer cycles were included. No significant differences in the number of obtained oocytes, total number of FET, and the total amount of gonadotropin were seen between the immediate and delayed fresh embryo transfer groups. The pregnancy outcomes of the two groups were similar. Conclusion: The duration of waiting time between failed fresh embryo transfer and the next FET does not affect pregnancy outcomes. Synopsis: The duration of waiting time between failed fresh embryo transfer and the next frozen embryo transfer does not affect pregnancy outcomes. [ABSTRACT FROM AUTHOR]