Effect of post-warming culture time on the live birth rate after frozen embryo transfer

Purpose: This study evaluated the influence of post-warming culture time on the live birth rate in day-3 and day-5 frozen embryo transfer (FET) cycles.

Methods: This multicenter, retrospective cohort study was performed at IVFMD, My Duc Hospital and IVFMD Phu Nhuan, My Duc Phu Nhuan Hospital in Vietnam between October 2019 and October 2020. Women who underwent FET cycles with the transfer of ≤2 day-3 or day-5 embryos were included in the study. FET cycles were divided into four groups based on the quartiles for the time between embryo warming and embryo transfer. The primary outcome was live birth after FET.

Results: Of 2548 FET cycles, 885 and 1663 cycles, respectively, had transfer of day-3 or day-5 embryos. Post-warming culture time ranged from 0.07 to 6.1 h. There were no significant differences between the post-warming culture time quartiles with respect to the number of embryos thawed, the number of embryos transferred, and the number of top-quality embryos transferred. Post-warming culture time was not significantly associated with the live birth rate in FET cycles using either day-3 or day-5 embryos.

Conclusions: Post-warming culture time did not affect live birth rate in FET cycles. Therefore, IVF centers should consider scheduling workflows to best suit the patient.