Preimplantation genetic testing in assisted reproduction

In the last years technologies have been developed that allow obtaining genetic information in less time and at lower cost, revolutionizing the genetic diagnosis in reproductive medicine, with availability of genetic tests from conception. High throughput sequencing analyses have increased the ability to detect embryos with genetic diseases, which has contributed to the better selection of embryos for in-vitro fertilization and, therefore, better reproductive outcomes. The preimplantation genetic testing (PGT) includes three subcategories of PGT for aneuploidies (PGT-A), PGT for single gene/monogenic disorders (PGT-M), and PGT for chromosome structural rearrangements (PGT-SR). This review provides an overview of the evolution of preimplantation genetic testing, the advantages and disadvantages of these technologies and their applicability in reproductive medicine as well as a description of the legislation and bioethics aspects. Advances in preimplantation genetic testing are changing clinical practice, posing new challenges for genetic counseling and alternative plausible to substantially reduce the risk of an adverse reproductive outcome related to the transfer of abnormal embryos. Despite the overall important implantation rates achieved following transfer of euploid embryos, PGT-A did not improve overall pregnancy outcomes in all women. There is a definite need for studies to identify the causes of why not all euploid embryos implant. Also, debate continues regarding the accuracy and the safety of this approach, and the currently available evidence is insufficient to support PGT-A in routine clinical practice. The general recommendation is that PGT-A, PGT-M and PGT-SR should be guided according to the antecedents of the couples.