Oocyte Quality Assessment in Assisted Reproductive Technology

Oocyte quality assessment constitutes a critical determinant of success in assisted reproductive technology, influencing fertilisation rates, embryo development and clinical pregnancy outcomes. Quality is underpinned by a combination of morphological integrity, cytoplasmic and nuclear maturation, biomechanical properties and molecular competence. Traditional morphological scoring encompasses evaluation of the zona pellucida, cytoplasmic granulation, polar body appearance and overall oocyte shape under light microscopy. Emerging methodologies probe subcellular dynamics, including spindle structure, mitochondrial distribution and autophagic flux, alongside non-invasive mechanical measurements of viscoelasticity at the zygote stage. Integration of high-throughput imaging, time-lapse morphokinetics and machine-learning algorithms promises enhanced objectivity, while molecular assays of follicular fluid metabolites and first polar body transcriptomes offer potential biomarkers of developmental competence. A comprehensive, multifaceted approach not only refines oocyte selection in in vitro fertilisation and intracytoplasmic sperm injection cycles but also guides targeted interventions to ameliorate age-related decline and optimise cumulative live birth rates worldwide.

Research from Nature Portfolio

Recent studies have demonstrated that measuring mechanical properties of the zygote within hours of fertilisation can serve as a non-destructive predictor of blastocyst formation. Zygotes exhibiting higher viscoelasticity correlate strongly with successful embryo development in both human and murine models, suggesting that oocyte maturation events imprint mechanical signatures on the cortex.

Further work has elucidated the predictive value of cytoplasmic granulation patterns in mature oocytes. Four distinct granulation distributions—fine, central, dispersed and uneven—were identified, each exhibiting significantly different fertilisation rates, embryo cleavage profiles and live birth outcomes. These patterns appear largely independent of maternal age and conventional embryo grading, underscoring the importance of upstream ooplasm morphology in embryo selection strategies.

Oocyte Quality Assessment in Assisted Reproductive Technology publication trend

The graph below shows the total number of articles in oocyte quality assessment in assisted reproductive technology across all publications each year (not limited to Nature Index journals).

Technical terms

Oocyte developmental competence: The intrinsic ability of an oocyte to undergo fertilisation and support embryo development to the blastocyst stage.

Autophagy: A cellular process that degrades and recycles cytoplasmic components, essential for organelle quality control in oocytes.

Mitophagy: Selective autophagic removal of damaged mitochondria, crucial for maintaining mitochondrial integrity during oocyte maturation.

Viscoelastic properties: Mechanical characteristics reflecting both viscous and elastic behaviour of the zygote cortex, predictive of embryo potential.

Morphological assessment: Visual evaluation of oocyte shape, cytoplasmic texture and polar body status under light microscopy.

Cytoplasmic granulation: Distribution pattern of granules within the ooplasm, indicative of cytoskeletal and organelle organisation.

Polar body: A small haploid cell extruded during meiosis, whose biopsy can provide molecular information on oocyte quality without compromising viability.

Zona pellucida: The glycoprotein layer surrounding the oocyte, whose thickness and uniformity influence fertilisation and embryo hatching.

References

1. VPS34 Governs Oocyte Developmental Competence by Regulating Mito/Autophagy: A Novel Insight into the Significance of RAB7 Activity and Its Subcellular Location. Advanced Science (2024).
2. Oocytes Quality Assessment—The Current Insight: A Systematic Review. Biology (2024).
3. Human oocytes image classification method based on deep neural networks. BioMedical Engineering OnLine (2023).
4. Human oocyte developmental potential is predicted by mechanical properties within hours after fertilization. Nature Communications (2016).
5. The Transcriptome of a Human Polar Body Accurately Reflects Its Sibling Oocyte*. Journal of Biological Chemistry (2011).
6. Relationship between the positions of cytoplasmic granulation and the oocytes developmental potential in human. Scientific Reports (2019).