Embryo selection is a common practice carried out in an effort to improve the efficacy of in-vitro fertilisation. Its aim is to select the best embryos for transfer, which appears to improve the efficacy. However, this is clearly eugenic practice , as it will allow some embryos to live for health reasons and others not. The best are transferred and given a chance to live, while the «less good» are discarded. However, and while recognising the non-ethicality of this practice, we consider it useful for our readers to re-examine current embryo selection techniques, in the light of a recently published review (Fertility Sterility 103; 333-341, 2015) .

Selecting embryos based on their morphology is the most widely used method, although it seems that embryos with similar morphology show different developmental capacity, which appears to indicate that this technique is not completely reliable.
Embryo morphokinetics is also employed, and appears to be able to somewhat improve the implantation rates when used jointly with the morphology study.
Another technique is chromosomal study of the embryos, which enables aneuploid embryos to be eliminated; aneuploidy is the leading cause of embryo loss and congenital defects in newborns.
There are two more techniques, metabolomics and proteomics, which have the advantage of being non-invasive, and which provide information on embryo quality. Metabolomics identifies the metabolite balance between the embryo and its culture medium; proteomics similarly identifies the protein balance between the embryo and its culture medium.
These are the techniques that are currently used to identify embryo quality. Nevertheless, morphological observation continues to be the most widely used method for selecting the best embryos. It appears though, that using the morphological appearance jointly with metabolomics and proteomics can obtain a significant improvement in embryo selection.This is all aimed, as we have already mentioned, at allowing those of better quality to live while discarding the rest, a clearly eugenic practice.