Cati
The Science

Scientific Fundamentals

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Abstract

We found that viability and genetic constitution are two relatively independent properties of early human embryos. With the help of time‑lapse technology, we are looking for the most viable embryo by monitoring morphokinetic properties and events. We use these events in our grading system to ensure a consistent embryo grading.

note

Many embryos can develop to term even if they are genetically altered

Viability

Viability of embryos correlates with their competence to implant and is expressed by their ability to develop to blastocyst stage in 5-6 days of in-vitro culture.

We distinguish between three groups of morphokinetic properties which have an impact on viability:

  • Morphokinetics indicating ability to produce relevant number of cells
  • Morphokinetics indicating differentiation of ICM cells into trophectoderm
  • Morphokinetics indicating embryo’s ability to hatch

Genetic constitution

Genetic constitution of embryos correlates with their competence to create a genetically healthy embryo. Genetic constitution of embryos is influenced by three (3) main factors:

  • Inherited diseases: Monogenic (X linked, dominant, recessive) gene disorders, translocations, etc. (the global incidence of simple-gene diseases at birth is close to 8 in every 10,000 liveborn infants)
  • Meiotic errors: Chromosomal/chromatid non-disjunctions, anaphase lack, etc. resulting in nuli-, mono-, trisomy, etc. Meiotic errors correlate with increased maternal age and alteration of spermiogenesis e.g. severe OTA syndrome or non-obstructive azoospermia in men.
  • Mitotic errors: Mitotic chromosomal malsegregations occurring due to abnormal cleavages resulting in chaotic complex aneuploidies. Mitotic errors are responsible for embryo developmental arrests, implantation failure and early miscarriages. It is estimated that approx. 80% of early human embryos are chromosomally aneuploid/mosaic as a result of abnormal mitotic divisions.
Note

Currently, inherited and meiotic genetic anomalies are not recognizable without preimplantation or prenatal testing. However, abnormal cleavages (the major source of mitotic aneuploidies responsible for developmental arrest, implantation failure and early miscarriages) can be detected by time‑lapse imaging.

Note

We currently do not monitor morphokinetics indicating mitotic errors.

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