PGT-M – genetic testing of embryos for single-gene disorders 

PGT-M (formerly PGD) is a method that makes it possible to rule out the risk of passing on serious genetic conditions to offspring.

Thanks to PGT-M, which is offered by Invimed, it is possible to examine the embryo’s DNA in detail and rule out or identify monogenic disorders such as cystic fibrosis, X-linked fragility syndrome or thalassaemia.

What is PGT-M testing?

PGT-M (Pre-implantation Genetic Testing for Monogenic Disorders) is a genetic test carried out on embryos prior to transfer as part of an in vitro fertilisation procedure. Its aim is to check whether the embryo has inherited a genetic mutation that could lead to the development of a specific condition, either one that runs in the family or one detected in the prospective parents during carrier screening.

Based on medical records, genetic test results and a case study, the specific condition for which the analysis will be carried out is determined. This makes it possible to reduce the risk of passing on a specific genetic condition to one’s offspring.

What conditions does PGT-M detect?

PGT-M is used to detect monogenic (single-gene) disorders, i.e. those caused by a change in a single gene. The test does not screen for all possible genetic disorders, but is targeted at a specific mutation previously identified in the family.

PGT-M can be used, amongst other things, in the diagnosis of conditions such as:

• cystic fibrosis,
• Huntington's disease,
• phenylketonuria,
• haemophilia
• and many other monogenic disorders.

This test is particularly recommended when one or both partners have been found to carry a genetic mutation, there is a history of a hereditary condition in the family, or previous genetic testing has indicated an increased risk of passing on a specific condition to a child.

How does PGT-A differ from PGT-M? 

These tests share a single objective: to rule out the presence of genetic abnormalities. The difference between PGT-A and PGT-M lies in the type of genetic abnormalities detected by each test. In the first test, we look for abnormalities in chromosome number – known as aneuploidy – which cause conditions such as Down’s syndrome, Edwards’ syndrome and Patau’s syndrome. In the second test (PGT-M), we screen the embryo for specific genetic disorders such as cystic fibrosis, phenylketonuria and Huntington’s disease. 

Why is it worth having PGT-M carried out? 

• Each test is tailored individually to each couple to best suit their genetic situation and needs. 
• It helps to select embryos that do not carry a genetic condition known to run in the family, before they are transferred to the womb. 
• If an Adventia-type test (link) confirms that you are a carrier of a genetic condition, it can help prevent the condition from being passed on to your child. 

Indications for PGT-M 

• The presence of specific monogenic disorders in one or both parents, or possibly amongst the partners’ family members, 
• the birth of a child with a single-gene genetic disorder, 
• carriage of single-gene genetic disorders, confirmed by testing for couples planning a pregnancy (e.g. Adventia). 

How does the PGT-M study work?

In its early stages, PGT-M embryo testing is carried out in the same way as PGT-A The embryo is cultured to the blastocyst stage, and a sample of the trophectoderm is collected via biopsy for analysis. 

The difference lies in genetic testing, during which a specific mutation in a gene is sought. It should be noted that, before the entire in vitro procedure begins, a case study is usually carried out, involving the submission of genetic material from the prospective parents – and often the grandparents as well – for genetic analysis, in order to determine the appropriate test to identify the mutation in question. 

How long does it take to get the result? 

The waiting time for PGT-M results depends on the type of condition being tested for and the scope of the test. The diagnostic process itself, following an embryo biopsy, usually takes up to 6 weeks. 

It is worth bearing in mind that, before the test begins, a case study must be carried out, during which the couple’s medical and genetic records are analysed and the scope of the diagnostic tests is determined. It is therefore advisable to start preparing for the PGT-M test well in advance of the planned in vitro procedure. 

Why PGT-M at Invimed 

Why is the pre-implantation genetic PGT test performed at Invimed incomparable to other centres in the country offering this test? 

At Invimed centres, we draw on many years’ experience in carrying out pre-implantation genetic testing. We have been performing PGT-M tests since 2005 – that is, for over 20 years. In addition, at Invimed we carry out a comprehensive assessment of the embryo’s genetic status. If no monogenic disorder is detected in the PGT-M test, we also carry out a PGT-A test to assess the correct number of chromosomes.  

Invimed works withIgenomix, a molecular genetics laboratory established in 1996 at the University of Valencia in Spain by a group of scientists. The group has extensive experience in conducting genetic research into human infertility. It is not only a laboratory providing diagnostic services, but also a research centre (Igenomix Research) and a foundation (Igenomix Foundation), whose aim is to translate scientific knowledge into reproductive medicine based on proven genetic expertise. 

Frequently asked questions

Bibliography

1. Good practice recommendations from the European Society of Human Reproduction and Embryology for pre-implantation genetic testing (PGT)
2. R. Kurzawa, R. Spaczyński, „Diagnosis and treatment of infertility. Standards of the Polish Society for Reproductive Medicine and Embryology and the Polish Society of Gynaecologists and Obstetricians.”