Preimplantation genetic testing

Preimplantation genetic testing enables the embryo to be checked for specific genetically inherited disorders carried by the future parents (cystic fibrosis, myasthenia, chromosomal translocation, etc.). It also identifies embryos with an abnormal number of chromosomes (including trisomy 21).

Preimplantation genetic testing involves examining the embryo before it is implanted into the woman’s body. The test reveals any genetic or chromosomal abnormalities in the embryo that could hinder the chances of pregnancy or present a significant risk to the future baby.

One advantage of preimplantation genetic testing is that it is performed before pregnancy, which avoids terminating the pregnancy if an abnormality is found in the embryo.

There are two main types of preimplantation genetic tests:

Preimplantation genetic test for monogenic/single gene defects (PGT-M)

This process involves analyzing the genetic material of an embryo created by IVF, before its transfer to the uterus, to avoid passing on a genetic disease carried by the future parents. According to the conditions set forth in the Federal Act on Medically Assisted Reproduction (RMA), it is only available to couples who carry a risk of a serious hereditary disease. Each case is subject to the approval of the multidisciplinary panel on preimplantation genetic testing, whose members include geneticists, experts in the field of medical ethics, reproductive medicine specialists, obstetricians, psychologists and specialists in the disease concerned.

Preimplantation genetic testing can be used to avoid hundreds of genetic conditions, but the diseases that are most commonly tested for worldwide are cystic fibrosis, Tay-Sachs disease, spinal muscular atrophy, haemophilia, sickle-cell anaemia, Duchenne muscular dystrophy and thalassaemia. It is also used to test patients with chromosomal disorders (for example, a reciprocal translocation). The procedure is then called PGT-SR.

Preimplantation genetic testing for aneuploidy (PGT-A)

This test is offered to certain infertile couples who are planning to start IVF treatment. It aims to detect anomalies in the number of chromosomes in the embryo’s cells. Aneuploidy (an abnormal number of chromosomes – either too few or too many – for example, trisomy 21) is a frequent cause of embryo implantation failure in utero. Preimplantation genetic testing for aneuploidy aims to optimize the chances of pregnancy by selecting embryos with the highest development potential.

PGT-A can be offered to women aged 35 and over, who have experienced recurrent implantation failures during previous IVF treatments, and have a history of miscarriages (more than two).

Preimplantation genetic testing for aneuploidy is also known as PGD-A.