Is early embryo development as observed by time-lapse microscopy dependent on whether fresh or frozen sperm was used for ICSI? A cohort study.

Purpose: The aim of this study was to compare timings of key events of embryo development from those originating from either fresh or cryopreserved ejaculate sperm using time-lapse technology.

Methods: In this retrospective observational cohort study, time-lapse technology was used to monitor 1927 embryos from 234 women undergoing intracytoplasmic sperm injection (ICSI) and utilizing either fresh (n = 172 cycles) or cryopreserved ejaculate sperm (n = 62 cycles) for insemination were included in the study. Key developmental events as described in time-lapse were compared with the use of generalized estimating equations (GEE) to adjust for any auto-correlation between the observations. In addition, multivariable logit regression models were used to account for any known baseline differences between the two groups.

Results: There were no differences in conventional embryo development such as number of 8-cell embryos by 72 h (p = 0.359), the number of blastocysts by 120 h (p = 0.417), and the number of top quality blastocysts (p = 0.956) between the two groups compared. There were no statistical differences in the timings of any of the key embryo developmental events (PN_t1, NEBD, cytokinesis, t2, t3, t4, t5, t6, t7, t8, tM, tSB, tEB, tHB, s1, s2, s3, cc2, and cc3) when either fresh or cryopreserved ejaculate sperm was used for ICSI. This was also confirmed with conventional morphological assessment.

Conclusions: This observational cohort study has shown that there are no differences in the morphokinetic parameters of early embryo development when either fresh or frozen ejaculate sperm are used for ICSI insemination.