Authorised by the Reproductive Medicine Act (RMA) since 1st September 2017, preimplantation genetic test – or PGT – offers new prospects for couples who carry serious diseases. Explanations by Dr Nicolas Vulliemoz, head of Fertility Medicine at CHUV.
“PGT-M”, “PGT-A”... What are we talking about?
In reality, when we talk about pre-implantation genetic testing, we need to make a distinction between two quite different situations.
On the one hand, there is pre-implantation testing for an anomaly on a single gene (PGT-M) or chromosome structure abnormality (PGT-SR) which involves analysing one gene, and on the other, pre-implantation genetic testing for aneuploidy (PGT-A) to detect possible chromosomal anomalies.
What does PGT-M involve?
For couples who are at risk of transmitting a serious genetic disease to their child, PGT-M consists of ovarian stimulation, as in the case of in vitro fertilisation, in order to obtain embryos. If the couple wants it and the conditions set out in the law are met, a genetic analysis is then carried out on the embryos’ cells to find out whether they are at risk of developing the disease or not.
The aim is only to transfer the embryos that are not at risk of developing the disease.
What does “serious (hereditary) disease” mean?
Within the meaning of the RMA, a serious disease is one that appears before the age of 50 and for which there is no effective and appropriate treatment. The option to use PGT-M before an embryo is implanted does not therefore exist in Switzerland for all genetic diseases but only for those that are considered “serious”.
How do you determine which diseases come within the scope of the RMA?
Our team has set up a multidisciplinary board (the PGT board), made up of doctors (fertility specialists and doctors specialising in the diseases concerned), biologists (in fertility medicine and genetic medicine), nurses, ethics specialists and lawyers, where each case is discussed on its own merits.
Each time we look at a new situation, we discuss whether we have the right to use PGT-M or not, depending on the criteria defined in the law and ethical principles.
What is “pre-implantation genetic testing for aneuploidy (PGT-A)”?
Theoretically, PGT-A – which is carried out to detect possible chromosomal anomalies – is aimed at infertile couples using in vitro fertilisation. It is used to select the best embryos to transfer.
A few cells are collected from the embryos obtained by in vitro fertilisation. Genetic analysis is then performed with the idea of not transferring embryos which have an abnormal number of chromosomes.
What are the advantages of PGT-A?
By selecting the best embryos, this technique helps to increase the chances of implantation when the embryo is transferred during the first cycle. Pregnancy may therefore occur more quickly. This approach also allows us to offer an elective transfer of a single embryo to patients of all ages and therefore reduces the risk of a multiple pregnancy. It also has the advantage of reducing the risk of miscarriage.
However, while PGT-A helps to select the best embryos, it doe not affect their quality in any way. The overall chance of pregnancy (in cumulative terms) in one course of IVF therefore remains unchanged.
Is PGT-A offered systematically?
We don’t offer PGT-A systematically but examine whether it is indicated depending on each couple’s situation, according to set criteria, such as failed implantations or the age of the mother. The wishes of each couple are also considered.
Are couples supported during these treatments?
Genetic counselling is obligatory before starting a PGT-M or PGT-A treatment. This is the time for the couple to discuss how these treatments are done and both their possibilities and their limitations. The consultation takes place at the CHUV, in the Genetic Medicine department.
At all times, the couples can also meet with our Psychological Support team. These treatments can generate a vast number of questions, and all our professionals are available to answer them.
Are these treatments paid for by the medical insurance schemes?
In Switzerland, medically assisted reproduction treatments (IVF, ICSI, thawing cycles and PGT) are not paid for by medical insurance schemes (basic and additional insurance). As a result, neither of these genetic tests is covered.
Cost issues are also discussed with couples during their consultation and they are given a financial estimate. If there are difficulties, we try to find solutions.
What training does your team need to have to obtain authorisation to perform PGT?
In 2016, Dr Marie-Pierre Primi, head of the Andrology and Reproductive Biology Laboratory (ARBL) and Dr Céline Leyvraz Recrosio, biologist, undertook specific training in PGT techniques in Spain and the United Kingdom.
In addition, Dr Pierre-Antoine Pradervand, clinical consultant, has come back from a two-year stay in Canada, where he undertook a training programme that allowed him to familiarise himself with these MAR techniques..
I myself also trained at the University of Oxford for almost three years, notably with the intention of introducing the practice of PGT to our centre.