Zygote Diameter and Total Cytoplasmic Volume as Useful Predictive Tools of Blastocyst Quality

Abstract

Introduction According to the Embryo Protection Act, the selection of embryos with the greatest potential for successful implantation in Germany must be performed in the pronucleus stage. The main aim of this study was to identify morphokinetic parameters that could serve as noninvasive biomarkers of blastocyst quality in countries with restrictive reproductive medicine laws.

Materials and Methods The sample comprised 191 embryos from 40 patients undergoing antagonist cycles for intracytoplasmic sperm injection. Blastocysts were cultured in an EmbryoScope chamber and video records were validated to determine the post-injection timing of various developmental stages, cleavage stages, and blastocyst formation. The Gardner and Schoolcraft scoring system was used to characterize blastocyst quality.

Results Morphokinetic data showed that the zygote diameter and total cytoplasmic volume were significantly different between good and poor blastocysts quality groups, where zygotes, which formed better blastocyst quality, had smaller diameter and smaller total cytoplasmic volume. Zygotes with more rapid pronuclear disappearance developed in better-quality blastocysts. Differences between good- and poor-quality blastocysts were also observed for late-stage parameters and for the spatial arrangement of blastomere where tetrahedral embryos more frequently forming good-quality blastocyst compare to the non-tetrahedral.

Conclusions The study findings could be used to enhance embryo selection, especially in countries with strict Embryo Law Regulations. Further studies, including those in which the implantation potential and pregnancy rate are considered, are warranted to confirm these preliminary results.

Zusammenfassung

Einleitung Gemäß dem Embryonenschutzgesetz muss in Deutschland die Selektion von Embryos mit dem größten Potenzial für eine erfolgreiche Einnistung im Vorkernstadium erfolgen. Das Hauptziel dieser Studie war es, die morphokinetischen Parameter zu ermitteln, die in Ländern mit restriktiven reproduktionsmedizinischen Gesetzen als nichtinvasive Biomarker für die Blastozystenqualität dienen könnten.

Material und Methoden Die Untersuchungseinheit bestand aus 191 Embryos von 40 Patientinnen, die sich einem Antagonisten-Protokoll zur Vorbereitung auf intrazytoplasmatische Spermieninjektionen unterzogen. Die gewonnenen Blastozysten wurden in einem EmbryoScope-Inkubator kultiviert, und die Videoaufnahmen wurden validiert, um die Zeitpunkte der verschiedenen Entwicklungsstadien und Spaltungsstadien nach der Injektion und die Blastozystenformation zu bestimmen. Um die Qualität der Blastozysten zu beurteilen, wurde das Gardner/Schoolcraft-Punktesystem verwendet.

Ergebnisse Die morphokinetischen Daten zeigten, dass es signifikante Unterschiede in den Durchmessern der Zygoten und im zytoplasmatischen Gesamtvolumen gab zwischen den qualitativ hochwertigen und den qualitativ minderwertigen Blastozystengruppen. Zygoten, die eine qualitativ hochwertigere Blastozyste bildeten, hatten einen kleineren Durchmesser und ein kleineres zytoplasmatisches Gesamtvolumen. Zygoten mit einem kürzerem Vorkernstadium entwickelten sich zu qualitativ hochwertigeren Blastozysten. Die Unterschiede zwischen qualitativ hochwertigen und qualitativ minderwertigen Blastozysten wurden auch bei Parametern der Spätstadien und bei der räumlichen Anordnung der Blastomere beobachtet, wobei tetrahedral angeordnete Embryos häufiger qualitativ hochwertige Blastozysten bildeten als Embryos ohne tetrahedrale Anordnung.

Schlussfolgerungen Die Ergebnisse dieser Studie könnten zur Verbesserung der Embryonenselektion verwendet werden, besonders in Ländern mit strengen Embryonenschutzgesetzen. Weitere Studien, die auch das Einnistungspotenzial sowie die Schwangerschaftsrate berücksichtigen, sind erforderlich, um diese Ergebnisse zu bestätigen.

Schlüsselwörter

Zygotendurchmesser - embryonale Morphokinetik - tetrahedrale Anordnung - Blastozystenqualität

Keywords

zygote diameter - embryo morphokinetics - tetrahedral arrangement - blastocyst quality

Publication History

Received: 21 November 2021

Accepted after revision: 13 June 2022

Article published online:
21 July 2022

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