Oocyte and embryo – how to evaluate and treat it to get the best results

The lecture by Marcos Meseguer answers the question of how an embryologist can move from subjective morphological grading to a reproducible prognosis and, on that basis, select the embryo with the highest implantation potential. Its premise is that visual assessment at isolated checkpoints is inferior to continuous observation of development, and that the transfer decision should rest on measurable parameters rather than on a single snapshot.

The foundation of this approach is time-lapse monitoring: an incubator with an integrated imaging system records embryo development without removing it from stable culture conditions. This preserves constant temperature, gas composition and pH while providing a complete temporal picture of cleavage, compaction and blastocyst formation. The speaker reviews the current capabilities of these systems and the data they make available for analysis.

The central concept of the lecture is morphokinetics — the timing of key developmental events: the appearance of pronuclei, division into two, four and more blastomeres, and the onset of compaction and cavitation. Deviations in these intervals and signs of abnormal cleavage, such as direct division from one cell into three, are associated with reduced embryo potential and serve as criteria for deselection.

Meseguer addresses the role of artificial intelligence in interpreting these data. Machine-learning algorithms process thousands of images and morphokinetic parameters, reduce inter-operator variability and produce a ranking of embryos by probability of success. Such an approach complements but does not replace the embryologist's expertise, leaving the final decision to the specialist.

A separate section is devoted to evaluating the oocyte as the starting point of the whole process. Oocyte quality largely determines the potential of the future embryo, so the morphology of the zona pellucida, the polar body and the cytoplasm, the state of the cumulus and the signs of maturity are analysed. The speaker shows how early oocyte characteristics relate to subsequent developmental dynamics and allow an earlier prognosis of the outcome.