Assessment of human embryos by time-lapse videography: A comparison of quantitative and qualitative measures between two independent laboratories

A total of 488 Day 3 human embryos with known implantation data from two independent in vitro fertilization laboratories were included for analysis, with 270 from Fertility North (FN) and 218 from Canberra Fertility Centre (CFC). Implanting embryos grew at different rates between FN and CFC as indicated in hours of the time intervals between pronuclear fading and the 4- (13.9 ± 1.1 vs. 14.9 ± 1.8), 5- (25.7 ± 1.9 vs. 28.4 ± 3.7) and 8-cell stages (29.0 ± 3.2 vs. 32.2 ± 4.6), as well as the durations of 2- (10.8 ± 0.8 vs. 11.6 ± 1.1), 3- (0.4 ± 0.5 vs. 0.9 ± 1.2), and 4-cell stages (11.8 ± 1.4 vs. 13.6 ± 2.9), all p<0.05. The application of a previously published time-lapse algorithm on ICSI embryos from the two participating laboratories failed to reproduce a predictive pattern of implantation outcomes (FN: AUC=0.565, p=0.250; CFC: AUC=0.614, p=0.224). However, for the qualitative measures including poor conventional morphology, direct cleavage, reverse cleavage and <6 intercellular contact points at the end of the 4-cell stage, there were similar proportions of embryos showing at least one of these biological events in either implanting (3.1% vs. 3.3%, p>0.05) or non-implanting embryos (30.4% vs. 38.3%, p>0.05) between FN and CFC. Furthermore, implanting embryos favored lower proportions of the above biological events compared to the non-implanting ones in both laboratories (both p<0.01). To conclude, human embryo morphokinetics may vary between laboratories, therefore time-lapse algorithms emphasizing quantitative timing parameters may have reduced inter-laboratory transferability; qualitative measures are independent of cell division timings, with potentially improved inter-laboratory reproducibility.