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The presence of cytoplasmic strings in human blastocysts is associated with the probability of clinical pregnancy with fetal heart

  • Assisted Reproduction Technologies
  • Published:
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Abstract

Purpose

Is the presence of cytoplasmic strings (CS) in human blastocysts associated with the probability of clinical pregnancy with fetal heart (CPFH) after transfer.

Methods

This case-control study involved 300 single blastocyst transfers. 150 of these resulted in a CPFH (cases) while 150 did not (controls). All embryos were cultured in Embryoscope+ and AI software (IVY) was used to select the blastocyst with the highest score from the cohort for transfer. An embryologist, blind to the transfer outcome, recorded the CS number, location, and duration of their activity.

Results

There was a significant difference in the number of blastocysts that contained CS, with 97.3% of women’s blastocysts resulting in +CPFH containing the CS compared to 88.7% of blastocysts in women who did not have a pregnancy (p = 0.007, OR; 4.67, CI 95% 1.5–14.2). CS appeared 2.4 h earlier in embryo development in the +CPFH group compared to their negative counterparts (p = 0.007). There was a significant difference in the average number of CS/blastocyst with a higher number being present in those that achieved a clinical pregnancy (mean: 6.2, SD 2.9) compared to those that did not (mean: 4.6, SD 3.0) (p ≤ 0.0001). There was a significant increase in the number of vesicles seen traveling along the CS with more seen in the blastocysts resulting in a +CPFH (mean: 4.3 SD 2.1) compared to those in the −CPFH group (mean: 3.1, SD 2.1).

Conclusion

This study has shown that the presence of cytoplasmic strings in human blastocysts is associated with the probability of clinical pregnancy with fetal heart.

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Data availability

http://handle.unsw.edu.au/1959.4/resource/collection/resdatac_1105/1

Code availability

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Author information

Authors and Affiliations

  1. IVFAustralia, PO Box 417, New Lambton, New South Wales, 2305, Australia

    Jessica Eastick, Christos Venetis, Simon Cooke & Michael Chapman

  2. University of New South Wales, Kensington, New South Wales, Australia

    Jessica Eastick, Christos Venetis, Simon Cooke & Michael Chapman

Authors
  1. Jessica Eastick
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  2. Christos Venetis
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  3. Simon Cooke
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  4. Michael Chapman
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Contributions

All authors contributed to the study conception and design. Material preparation, data collection, and analysis were performed by Jessica Eastick, Christos Venetis, Simon Cooke, and Michael Chapman. The first draft of the manuscript was written by Jessica Eastick and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Corresponding author

Correspondence to Jessica Eastick.

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Ethics approval

This is an observational study. The IVFAustralia Research Ethics Committee has confirmed that no ethical approval is required.

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The authors declare no competing interests.

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Key message

For the first time, this case-control study has shown that the presence of cytoplasmic strings in human blastocysts is associated with clinical pregnancy with fetal heart following embryo transfer.

Supplementary information

ESM 1

(DOCX 13 kb)

Supplementary Video 1

A timelapse video exported from the Embryoscope+ showing the same day 5 blastocyst as seen in Fig. 2a–e. A single cytoplasmic string can be seen traversing the blastocoel cavity between 104.8 - 107 hpi. It connects the ICM and the TE cells. A single vesicle can be seen emerging from the TE cells and as the blastocyst develops and expands, the single vesicle moves along the cytoplasmic string. Another vesicle emerges from the TE cells and these vesicles continue to move along the cytoplasmic string from the TE cells to where they are delivered to the ICM and absorbed. This process takes a total of 2.2 h to occur. (AVI 859 kb)

Appendix

Appendix

Table 6 Morphokinetic markers assessed for blastocysts that were transferred, which resulted in a clinical pregnancy with a fetal heart, compared to the control group
Full size table

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Eastick, J., Venetis, C., Cooke, S. et al. The presence of cytoplasmic strings in human blastocysts is associated with the probability of clinical pregnancy with fetal heart. J Assist Reprod Genet 38, 2139–2149 (2021). https://doi.org/10.1007/s10815-021-02213-1

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  • DOI: https://doi.org/10.1007/s10815-021-02213-1

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