Survival Rates and Clinical Effectiveness of Vitrified Human Blastocysts in the Practice of Embryological Laboratories

Objective – to carry out comparative analysis of embryo survival and pregnancy rate after the vitrification of human embryos at different stages of the preimplantation development.

Material and methods. A total of 1311 embryos were analyzed. For vitrification of embryos, the Irvine Scientific media (USA) and the CryoTop open-type carriers (Japan) were used. The vitrification and the defrosting of embryos were carried out according to the manufacturer's recommendations. The statistical processing of the results was performed on a computer in the statistical computing environment R (R V. 3. 5. 3, RStudio V. 1. 1. 463), the primary data entry was performed using MS Excel spreadsheets. We used methods of descriptive statistics, tests for comparing proportions, including an accurate binomial test for small samples and a single-sample test of proportions with continuity correction for large samples.

Results. The range of the embryo survival is quite wide and ranges from 75% to 100%. When conducting a detailed analysis of the dependence of the pregnancy rate on the stage of cryopreserved blastocysts, we found a direct link between the clinical indicators and the structure of the embryos of 5–6 days of the preimplantation development. The blastocysts with the highest degree of the internal cell mass and the trophoblast formation in combination with a high degree of the expansion (4) give the best results of the clinical pregnancy rate.

Conclusions. When performing vitrification we found out that the stage of the blastocyst development influences their survival and pregnancy rates. The phenomenon of hatching in the embryos of 5–6-day preimplantation development should be regarded as a factor that reduces the success of vitrification.

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