Preimplantation Genetic Testing for Aneuploidy (PGT-A)

Definition - What does Preimplantation Genetic Testing for Aneuploidy (PGT-A) mean?

Preimplantation genetic testing for aneuploidy (PGT-A), is a genetic test done to identify embryos with an abnormal number of chromosomes (known as aneuploidy) that are less likely to lead to a viable pregnancy. Embryos identified as abnormal are not selected for transfer to a uterus.

The older terminology used for PGT-A is PGS (preimplantation genetic screening).

FertilitySmarts explains Preimplantation Genetic Testing for Aneuploidy (PGT-A)

Normal embryos contain 46 chromosomes. Aneuploid pregnancies (having too many or too few chromosomes) represent the vast majority of pregnancy failures, especially in women with advancing age. PGT-A offers a way to overcome this age-related rise in chromosomal abnormalities and drop in fertility.


  • Enables transfer of the single best embryo, which minimizes the risk of multiple pregnancies and other pregnancy complications such as premature or low birth weight deliveries.
  • Improves successful implantation rates.
  • Curtails the miscarriage rates and pregnancy failures.

PGT-A can be done for most individuals or couples undergoing IVF. However, because the odds of having chromosomally abnormal embryos greatly increase as a woman ages, the test is most ideal for this age group.

PGT-A involves testing of the biopsied cells taken from the outer layer of the developing embryos (ideally on day 3), analyzing the genetic makeup of these cells, and transferring only the best embryos.

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