Is there a better evolutionary outcome in a 4-cell tetrahedron embryo?

Marta Ribeiro Hentschke,Catarina Heckmann Petracco,Victória Campos Dornelles,Ricardo Azambuja,Rishabh Hariharan,Mariangela Badalotti,Isadora Badalotti Telöken,Bibiana Cunegatto,Fabiana Mariani Wingert,Cristina Hickman,Alvaro Petracco

doi:10.5935/1518-0557.20210034

Abstract

With the growing understanding of in vitro fertilization and reproductive technology, the magnitude of studies related to embryonic evolution has also increased. The optimization of embryo selection is crucial to minimize the risk of multiple pregnancies and to guarantee successful implantation and pregnancy. On the second day of culture, the four-cell embryo can be shaped into different arrangements, such as tetrahedral and planar. Previous studies have shown that mammalian embryos have a tetrahedral shape and that any deviation from this ideal configuration can negatively affect blastocyst development. A few studies have also found that planar embryos would be linked to negative predictors of success for reaching the blastocyst stage and its good quality. Therefore, it seems that tetrahedral should be preferred over planar-shaped embryos for embryonic transfers, but there is still little understanding and evidence about this subject. Thus, the objective of the present paper was to review the available literature on study tendencies to compare tetrahedral and planar-shaped embryos considering their effect on implantation and pregnancy results.

Highlights

After Louise Brown’s birth, Steptoe et al (1980) showed that in vitro fertilization (IVF) success rates were 6% per cycle
It is this constant desire for improved outcomes and an increased emphasis on minimizing the risks of multiple pregnancies that stresses the importance of optimizing the embryo selection stage - a stage which is highly compatible with the implementation of artificial intelligence (AI) (Figueira, 2017)
It is still unknown whether there is a positive impact on using AI, since the difference in the correlation between the choice of embryo made by embryologists and pregnancy rates is still not well established in the literature (Gardner et al, 2015)

Summary

Introduction

After Louise Brown’s birth, Steptoe et al (1980) showed that in vitro fertilization (IVF) success rates were 6% per cycle. Greater knowledge about gametes’ physiology and their behavior, as well as improved laboratory conditions, have yielded better embryonic potential and fertilization rates Despite these significant advances, there remains a growing interest in analyzing the predictive ability of specific events occurring during embryonic evolution to improve both embryonic implantation and clinical pregnancy rates. The implementation of AI into a time-lapse operating system may enable a constant evaluation of morphological characteristics throughout the embryonic development, using parameters (e.g. pixel values) that are otherwise inconspicuous to the human eye. This allows for the possibility of an AI and time-lapse system capable of embryo classification. Among the embryonic factors under study, the embryonic cells’ arrangement, when the embryo presents itself with a count of four blastomeres, has been gaining increased attention. Gulyas (1975) demonstrated that rabbit 4-cell embryos might be arranged in a tetrahedral or non-tetrahedral arrangement, one of these later described as planar (Gulyas, 1975; Ebner et al, 2012)

Objectives

Findings

Conclusion