Is the polar body approach best for pre-implantation genetic screening?

Pre-implantation genetic screening is carried out with the aim of selecting oocytes or embryos that have the optimal chance of producing an ongoing pregnancy by eliminating those that have a detectable chromosomal anomaly. A variety of cells may be chosen for testing; the first polar body, with or without the corresponding second polar body, a single blastomere from a cleavage stage embryo or a group of cells from the trophectoderm at the blastocyst stage. This paper explains the different stages when aneuploidy may arise during oocyte development and the contribution made by post-zygotic aneuploidy to the overall burden as a basis for understanding the arguments for and against selecting polar bodies as the cells of choice for pre-implantation screening.