The "mosaic'' embryo: misconceptions and misinterpretations in preimplantation genetic testing for aneuploidy

Preimplantation genetic testing for aneuploidy (PGT-A) remains one of the most controversial topics in reproductive medicine. With more than 40% of in vitro fertilization cycles in the United States reportedly involving PGT, both those in favor of and those opposed to PGT-A have significant interest in the efficacy of PGT-A. Ongoing issues include what patient population, if any, benefits from PGT-A, the true frequency of chromosomal mosaicism, whether embryonic aneuploidies self-correct, and how practitioners manage embryos designated as "mosaic."This review addresses several misconceptions and misinterpretations of data surrounding the genetic analysis and prediction of mosaicism in the preimplantation embryo. ((C) 2021 by American Society for Reproductive Medicine.)