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 typically not selected for transfer to a uterus.
The older terminology used for PGT-A is preimplantation genetic screening (PGS).
FertilitySmarts explains Preimplantation Genetic Testing for Aneuploidy (PGT-A)
Normal embryos contain 46 chromosomes. Aneuploid pregnancies (having too many or too few chromosomes) are thought to represent the vast majority of pregnancy failures, especially in women with advancing age. PGT-A offers a way screen for this age-related rise in chromosomal abnormalities and decrease in fertility.
Benefits of PGT-A:
- Enables advanced screening and possible transfer of a single euploid embryo (if available), which minimizes the risk of multiple pregnancies and other pregnancy complications such as premature or low birth weight deliveries.
- Transferring a screened and normal embryo (if available) improves successful implantation rates.
- Curtails the miscarriage rates, pregnancy failures and viable pregnancies with chromosomal abnormalities (like trisomy 21 or Down’s Syndrome) by identifying which embryos carry aneuploidies.
Who is PGT-A for?
PGT-A can be performed 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, couples who have a history of abnormal pregnancies or losses and for couples that have a sex-linked genetic disorder.
How is PGT-A done?
PGT-A involves testing of the biopsied cells taken from the outer trophectoderm layer of the developing embryos, analyzing the genetic makeup of these cells, and transferring balanced or normal embryos (if available).
- Preimplantation Genetic Screening: A Practical Guide. (2013).
- Preimplantation Genetic Testing. (2014).