According to Dr. Kuttner preimplantation genetic testing (PGT) comprises a group of genetic tests used to evaluate embryos before transfer to the uterus. The goal is to try to identify genetically normal vs abnormal embryos and only transfer the normal embryos to the uterus. Dr. Kuttner warns that PGT is not 100% perfect in diagnosing embryos with or free of all genetic abnormalities. As with any test false-positive and false-negative results are possible and thus patients need to know the results do not guarantee an abnormal or normal genetic embryo.
Consequently, conventional pregnancy screening and diagnostic testing should be offered and performed on pregnant women, even those who underwent PGT.
Preimplantation genetic testing has evolved from its start when only a handful of chromosomes could be studies and only for a few abnormalities. Preimplantation genetic testing-monogenic (known as PGT-M) is targeted to single gene condition. Preimplantation genetic testing-monogenic uses only a few cells from the early embryo, usually at the blastocyst stage, and misdiagnosis is possible but rare. To detect structural chromosomal abnormalities such as chromosome gains and losses related to parental structural chromosomal abnormalities (eg, translocations, inversions, deletions, and insertions), PGT-structural rearrangements (known as PGT-SR) is used. The main purpose of preimplantation genetic testing-aneuploidy (known as PGT-A) is to screen embryos for whole chromosome abnormalities including the 22 pairs of autosomes and the sex chromosomes X and Y. Conventional screening and diagnostic testing for genetic abnormalities should be offered to all pregnant women who have had preimplantation genetic testing accordance with ACOG recommendations.
