Status of preimplantation genetic testing and embryo selection

At the recent 2018 PGDIS congress, a review of randomized controlled trials of preimplantation genetic testing for aneuploidies (PGT-A) showed improved ongoing pregnancy rates per transfer in experienced centres and in women aged 35 years and older. Young women produce 40% abnormal embryos (20-60% range), but not all centres see a selection advantage; this indicates the need for more emphasis in improving biopsy and case management. Some chromosome abnormalities are iatrogenic; PGT-A could, therefore, be used as assisted reproductive technology (ART) quality control. Great improvements in non-invasive PGT by testing spent media have been reported, ranging from 80-95% concordance with trophectoderm biopsy, probably precluding the need for biopsy soon. Mosaicism was widely discussed, with PGDIS agreeing to update their guidelines, but continuing to recommend prioritizing euploid, followed by mosaic embryos. Techniques to allow simultaneous single sample analysis of aneuploidy and inherited mutations are improving, but this does not extend to de-novo mutations. Convincing data were presented on the efficacy of using endometrial receptivity tests to improve ART outcomes adjuvant or independently of PGT-A. Imprinting, CRISPR and cloning were also discussed, with a concluding presentation on the first extensive data (aneuploidy and morphology) on in-vivo conceived embryos.