Preimplantation genetic testing

About 2% of the couples are at risk of having a child affected from an inheritable monogenic condition, and several women attempting to conceive are of advanced maternal age (≥35 yr), therefore subject to an increased risk of obtaining aneuploid blastocysts (from 30% to 50%–90%). Couples carrying a structural rearrangement (e.g., translocations), then, face an even higher risk of producing aneuploid gametes, independently of woman age. To date, preimplantation genetic testing (PGT) has been introduced to identify embryos affected from monogenic condition (PGT-M), chromosomal structural rearrangements (PGT-SR), or chromosomal aneuploidies (PGT-A) in a cohort of embryos produced during an in vitro fertilization (IVF) cycle. Its application worldwide allowed a higher efficiency and safety in the management of IVF, avoiding the risk of transferring affected and/or chromosomally abnormal embryos, reducing the risk for miscarriages and more confidently applying an elective single embryo transfer policy. Clearly, expert operators and well-equipped laboratories are required to safely conduct blastocyst culture, trophectoderm biopsy and vitrification, as well as validated platforms to conduct molecular analyses. This chapter represents an overview of PGT from its theorization to the most promising future perspectives.