New insights from time-lapse imaging

Published 23 July 2019

In this second review of embryology sessions in Vienna, we report from a selected oral communications session on time-lapse imaging. Six speakers presented their data on embryo assessment using various morphokinetic parameters to support their predictive value in embryo selection for transfer.

This session - Session 34 - featured the first study to ever correlate embryo development and pregnancy outcomes with cytoplasmic halo characteristics. Dr Ezoe from Tokyo  reported that among 1009 single-blastocyst-transfers the presence of halo, recorded between the second polar body extrusion and first cell division, and its characteristics were associated with cleavage pattern, blastocyst formation, and ongoing pregnancy. In their dataset, 88% of fertilised oocytes presented a halo and exhibited significantly lower rates of direct cleavage, reverse cleavage and asymmetrical division compared with embryos derived from halo-absent zygotes.

Dr Foong from Canada showed results from a Phase IV randomised controlled trial on the use of automated time-lapse microscopy for embryo selection. The study used the Eeva time-lapse test to define the precise timing of cell division and to predict the likelihood of an embryo developing to the blastocyst stage. The trial included 899 subjects randomised to conventional morphological grading or Eeva. Although Eeva predicted blastocyst formation at the cleavage stage with a specificity of 85%, the implantation rate did not differ between the two trial groups. 

A study from Dr Chaput and colleagues from Clermont-Ferrand and Paris was described as the first quantitative analysis of compaction (disappearance of cell boundaries) in human embryos and its relevance in implantation. Although the French group developed an elegant strategy to describe the dynamics and quantify the geometrical parameters of compaction, no correlation between compaction and implantation success was observed across the 224 blastocysts analysed after IVF or ICSI. 

A study from Japan aimed to discover whether the size of the male and female pronuclei analysed by measuring their vertical and horizontal diameters might correlate with the incidence of live birth. In a retrospective study of 213 single blastocyst transfers from ICSI and IVF, they standardised those characteristics correlating with a live birth. One of them was the presentation of a cut-off value of approximately 40 microns squared describing the difference in the size between the two pronuclei just before the breakdown of their membrane. Because PGT in Japan is not permitted, this methodology could be employed to secure the transfer of a healthy embryo.

The impact of the striking reverse cleavage (RC) phenomenon on in vitro development and reproductive outcomes was discussed by J.M. Capdevila from Spain. RC is thought to be a part of a cellular error-detection mechanism, and embryos capable of overcoming this checkpoint are believed to have good prognosis. In a retrospective study of 23,340 embryos, Dr Capdevila and colleagues recorded 13% of RC events on day 2 or 3. However, the RC rate resulting in a good quality blastocyst stage had comparable reproductive outcomes with embryos without RC.

The last presentation addressed the question whether nucleation error phenotypes (NEP) during first cleavage - such as the presence of multiple nuclei per blastomere, traditionally believed to be a poor prognosis marker - could predict implantation and live birth. A Norwegian study presented data from 2082 transfer cycles in which 22.9% of embryos with NEP at the 2-cell stage had lower implantation and live birth potential - but only when the results were not stratified according to type of NEPs and infertility diagnosis.

There were a number of important findings in this session, and a fully packed and interactive auditorium endorsed the value of time-lapse imaging as an additional tool for the assessment of embryo development.