Until a few years ago this genetic study was carried out through FISH technique (Fluorescence In Situ Hybridization). This technique could only allow to analyze a limited number of chromosomes in the biopsied cell, which varied between 5 to 12 from the total 23 pairs of chromosomes that human species has, so a great part of the embryo chromosomes remained without being analysed. The `normal´ embryos from the analyzed chromosomes and those of better morphology were selected for the transfer to the uterus. However, the results obtained so far were not unanimous for the different clinic indications, and, in general, it was observed that the rate of pregnancy or the rate of baby born did not increase, as it was to be expected.
From 2009 the analysis of embryonic cells started to be used, Array technique of Comparative Genomic Hybridization (CGH). Array CGH is a technique for genetic analysis, which detects losses or gains of the genomic regions that can appear in a sample of DNA in a global way, that is, it studies the whole genome at the same time, without selection or bias. The Array CGH helps us to solve the limitations of FISH, becoming a powerful tool that permits a trustworthy analysis of the 23 pairs of chromosomes. In the last years similar techniques to Array CGH have been emerging, for example, the KaryoLite BoBs, which allows us to analyse the chromosomes at a high resolution and in an automatic way.