Changes in sequencing technology used for preimplantation genetic testing for aneuploidy.

The continued development of assisted reproductive technologies has aimed to improve pregnancy outcomes through screening methods for the identification of embryos with monogenic disorders, chromosomal aneuploidy or structural abnormalities. There is an increased risk of chromosomal abnormalities for patients with advanced maternal age, recurrent implantation failure and recurrent pregnancy loss. To address this, preimplantation genetic testing for aneuploidy has evolved through several methods since the 1990s, when it first began through fluorescence in situ hybridisation. The limitations of these early methods were overcome with the progression in technology that enabled the screening of all 23 chromosome pairs. These methods included microarray methods and next-generation sequencing platforms. Currently, these are used for PGT-A; however, for IVF clinics to carry out PGT-A utilising these methods, samples are sent to external laboratories capable of carrying out these methods. More recently, nanopore sequencing has emerged, which may overcome these limitations and be carried out within IVF clinics to facilitate faster patient results. This review focuses on the evolution of PGT-A methods through next-generation sequencing and the current status of these methods.