Fertilization Time and Oocyte Spindle Integrity: Implication for Embryo Ploidy
In brief
Visible spindle in oocytes triples euploid embryo rate to 42%
In a retrospective ART study, oocytes showing a meiotic spindle by polarized light yielded euploid embryos in 42% of cases versus only 14% when the spindle was absent or misaligned. Extending the trigger-to-ICSI interval to 40-44 hours further raised euploidy to 47% compared with 33% at 36-39 hours, suggesting spindle visibility and timing improve ploidy prediction, especially in older women.
- Journal
- Reproduction & fertility (Q1)
- Published
- 24 July 2026
- Study design
- Cohort / observational study
- Evidence level
- Level 3, Low (CEBM 3b)
- Authors
- Irena Kratochvilova, Olga Tepla, Anna Pšeničková, Jan Kybic, Denis Baručić, Kateřina Veselá, et al.
- PMID
- 42496869
- DOI
- 10.1530/RAF-26-0016
Why clinicians should know about it
- Picked for Embryology (paper of the day, 25 July 2026): Spindle visibility predicts oocyte maturity and embryo ploidy
Abstract
The aim of this retrospective study in assisted reproductive technology was to provide new evidence that: (1) visibility of the meiotic spindle (MS) in human oocytes with an extruded first polar body predicts not only nuclear maturation but also embryo ploidy; and (2) the interval between ovulation triggering and ICSI-mediated fertilization affects the chromosomal status of embryos. MS visibility was assessed using polarized light microscopy, and the trigger-to-fertilization interval was adjusted accordingly to increase the likelihood of complete oocyte nuclear maturation. Extending the trigger-fertilization interval based on MS status significantly increased the proportion of mature oocytes (displaying both MS and polar body) from 79% to 92% (p < 0.05), indicating ongoing spindle assembly. Of 1,879 oocytes examined under polarized light, 462 (24.5%) developed into embryos undergoing PGT-A. Embryos derived from immature oocytes (without visible MS or with a spindle bridge to the polar body) had a euploidy rate of 14%, compared with 42% in embryos from mature (visible MS) oocytes (p < 0.05). Differences in embryo euploidy were also associated with the interval between ovulation trigger and ICSI fertilization. Cycles with a trigger-ICSI interval 40-44 hours had a significantly higher likelihood of euploidy (47%) compared with cycles in which the trigger-ICSI interval was 36-39 hours (33%) (p < 0.05). Namely in women of advanced maternal age, who exhibit an increased risk of embryonic aneuploidy, spindle-guided assessment of oocyte maturation and quality may improve the prediction of subsequent embryo ploidy.
Abstract as published, via PubMed.
For healthcare professionals. The summary is generated by AI from the published abstract, and the evidence level is assigned automatically from the study design on the Oxford CEBM hierarchy. Neither is medical advice. Read the full paper before changing practice.