Preimplantation genetic testing for aneuploidy (PGT-A, formerly PGS) detects chromosome copy number abnormalities of embryos and is an effective method for selecting the best embryos. The test helps identify embryos with a normal chromosomal complement, supporting more informed embryo selection for transfer.
Selecting chromosomally normal embryos can improve pregnancy outcomes and reduce the risk of miscarriage. PGT-A is particularly beneficial for women over the age of 35, as well as for patients with recurrent pregnancy loss or repeated unsuccessful fertility treatments. In general, transferring embryos with a normal chromosome number is associated with higher implantation rates and better treatment outcomes across all age groups.
Even in young women, around 40–50% of embryos that appear morphologically normal may have an abnormal number of chromosomes (aneuploidy). In women over 40, this proportion may increase to as high as 75–90%.
Most chromosomal abnormalities prevent normal embryo development or lead to an early miscarriage. However, there is considerable variation between individuals, and unsuccessful fertility treatments are not always caused by chromosomal abnormalities.
Out of a young woman’s normal looking embryos, 40–50% may have an abnormal number of chromosomes in a cell, i.e. be aneuploid, while for women over 40 this figure may be as high as 75–90%.
The majority of chromosomal abnormalities lead to arrested development of the embryo or an early miscarriage. However, variation between patients is high, and unsuccessful treatments are not necessarily a result of chromosomal problems.
Source: US CDC/SART (left), Harton et al. (2013) Fertility and Sterility 106:1695-703 (right)
In PGT-A treatment, a small sample of approximately 5–8 cells is taken from a five- to seven-day-old embryos at the blastocyst stage. After the biopsy, the embryos are frozen using vitrification. Once the genetic analysis is complete, embryos with a normal chromosome number can be thawed and transferred to the uterus.
Embryo chromosome testing helps identify embryos with the best chance of leading to a successful pregnancy and may reduce the number of unsuccessful embryo transfers. On average, the chance of pregnancy after transferring a chromosomally normal embryo is up to around 50%, and the risk of miscarriage is lower than with untested embryos.
Taking a small cell sample from the embryo carries a very low risk of affecting embryo viability. To avoid this entirely, we also offer non-invasive chromosome testing (niPGT-A, Non-Invasive Preimplantation Genetic Testing for Aneuploidy). This method analyzes DNA released by the embryo into the culture medium, without the need for a biopsy.
During PGT-A treatments, embryos are cultured in EmbryoScope® time-lapse incubator, which allow continuous monitoring of embryo development and support more accurate embryo selection.
Please contact us if you would like to learn more about Ovumia’s PGT-A and niPGT-A treatment options.
