PGT-A: Preimplantation Genetic Testing for Aneuploidy

Preimplantation genetic screening was earlier known as preimplantation genetic screening and offers insight into the number of chromosomes within IVF embryos. Normal chromosome results will have higher chances of achieving a normal and successful pregnancy.

Potential PGT-A Results

The results of PGT can be one of the three – normal, mixed, and aneuploid. In the first case all the cells have normal chromosomes, while in the second case its partly normal and partly abnormal. An aneuploid result means that all the cells that have been tested have returned negative results.

Euploid Mosaic Aneuploid
Number of chromosomes per cel Normal Mixed All abnormal cells
Chances of Successful Pregnancy High Intermediate Low
Transfer Priority High Intermediate Low


Aneuploidy and Age

In theory, anyone can produce aneuploid embryos; however, in reality it has been observed that the risk of producing aneuploid embryos increases proportionally with increasing women’s age. Given that aneuploid embryos are associated with increased implantation failure and miscarriage and lower live birth results, it can be concluded that increasing age results in fewer successful implantations and pregnancies.
At the age of 35 or less, there is only a one-third possibility of an aneuploid embryos while the same at the age of 40 doubles to almost 60%. And further increase in age has even higher possibilities with 42-year olds having an 80% chance of aneuploid embryos.

The PGT-A Process

Preimplantation testing for aneuploids is a part of the IVF process and involves four distinct steps. Firstly, it is the IVF process itself wherein the embryos are retrieved and then the embryologist removes some cells from the part of the embryo that is expected to go on and become the placenta. Following the retrieval of the cells from the embryo, they are tested in a genetic lab. The final step is the transfer of the embryos into the uterus following a successful result and discussion with the patient.

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