ABSTRACT
Preimplantation genetic testing for aneuploidies (PGT-A) is the most common, and arguably the most controversial, application of PGT. It is applied to prevent live births of aneuploid offspring, to reduce miscarriage rates, and improve IVF outcomes. Referral categories include advanced maternal age, recurrent miscarriage, recurrent implantation failure, and male factor infertility. First applied clinically in the 1990s, it has utilized a range of technical approaches, e.g., FISH, qPCR, aCGH, karyomapping, and NGS. Sampling approaches reflect other PGT applications (polar body, cleavage stage, blastocyst), with the latter now the most popular, with significant prospects for noninvasive approaches. Often coupled with “freeze-all” strategies, it is widespread but controversial, in part because of the issue of mosaicism. The extent to which a biopsy diagnosed as (partially) aneuploid reflects the karyotype of the whole embryo (and hence its ability to develop into a normal live birth) is still the subject of considerable debate. Cohort studies and randomized trials attest to the efficacy of PGT-A; however, critics question the rigor with which these studies are designed and performed. The role of mitochondrial DNA and time lapse in the detection of aneuploidy is discussed, as is how these technologies allow us to gain invaluable insights into early human embryonic development.
