Comparative genomic hybridization (CGH)
The development of array Comparative genomic hybridization (a-CGH) for preimplantation genetic diagnosis (PGD) provides useful information on the frequency and type of aneuploidies in gametes and embryos. The technique can be applied at the stage of the mature oocyte (biopsy of 1st polar body), zygote (biopsy of 1st and 2nd polar bodies), day-3 embryo (biopsy of one blastomere) or blastocyst (trophectoderm biopsy).
a-CGH gives us the ability to screen all chromosomes, contrary to the technique of FISH, which evaluated only a limited number of chromosomes. a-CGH showed that 20-30% of oocytes are aneuploid in women aged 20-30, while aneuploid oocytes from women over 40 are 50-80%.
The method of FISH can detect chromosome abnormalities only in 20-40% of embryos. On the other hand, a-CGH can successfully detect 85% of aneuploid embryos and 89% of aneuploid oocytes, significantly increasing the chance of implantation of a selected embryo.
Therefore, PGS using a-CGH is an important development of molecular genetics. The technique can lead to increased pregnancy rates because it can detect chromosome abnormalities with high accuracy, resulting in the transfer of healthy embryos.