Every expectant mother and father wants their child to be born healthy. Thanks to genetic testing of embryos, problems can be detected in time and healthy embryos can be implanted.

PGD has been shown to increase the success rate of live births. Unfortunately, the most common cause of recurrent miscarriages in the first third of pregnancy is usually genetic problems.

Unfortunately, PGD/PIS is not available to all parents in Europe. Last year, the law in Switzerland changed slightly so that couples with proven genetic problems are allowed to have some tests, but only after they have had several proven miscarriages. However, all other couples who want to test as a precaution are not allowed to do so.

In selected IVF clinics abroad there are no restrictions, so their success rates are also higher.

What is the difference between PGD and PIS?

Preimplantation genetic diagnosis (PGD or PGT-M) is carried out for parents with a genetic burden. It is suitable if one or both partners in the family have a genetic disease. In this diagnostic procedure, doctors focus on the chromosomes that carry information about the defect. They then select only embryos that have not inherited the defective genes for transfer to the uterus.

In pre-implementation genetic screening (PIS or PGS or PGT-A), healthy partners are selected because they want to be screened. Often these are parents who have already had one or more IVF treatments without becoming pregnant. In some countries (e.g. Northern Cyprus) this method is used to select for X or Y chromosomes. This means that they can name the sex of the child based on these tests.

What can PGS detect?

PGS can be used to detect chromosomal defects such as Down's syndrome (trisomy 21), Edwards' syndrome (trisomy 18), Pätau's syndrome (trisomy 13), Turner's syndrome (monosomy X), Klinefelter's syndrome (trisomy XXY).

How does PGD and PGS work?

Clinics wait 72 hours after fertilisation, when the embryo already has a larger number of cells. They take one or more cells and analyse them. The embryo is not damaged by the procedure and continues to develop normally.

The geneticist will give you the results within 48 hours. After evaluation, the doctor will make a recommendation.

Not all diseases can be detected by PGD. There are diseases or conditions where the cells are called mosaics. This means that the disorder is only present in a few per cent of the cells. In this case, it depends on which cells the geneticist puts under the microscope for PGD. There are also very rare diseases that have not been studied. My doctors are happy to give me a list of possible tests. Fortunately, these cases are very rare.

PGD cannot replace PIS. With PGD, only diseases known to run in the family are monitored.

Doctors recommend PGD or PGS in the following cases

1. Repeated miscarriages.
2. Frequent unsuccessful IVF cycles.
3. Previous birth or miscarriage of a baby with a chromosomal defect.
4. Age risk (maternal age over 36 years).
5. Sex-related defects, if individuals of the unaffected sex are appropriately selected.
6. In the case of sperm obtained by surgical extraction (MESA/TESE).
7. One of the parents is a carrier of the specific gene shift.
8. Some common genetic diagnosable diseases are cystic fibrosis, fragile X syndrome, haemophilia, thalassemia, sickle cell anaemia, phenylketonuria, mutation of tumour suppressor gene.
9. In couples where only a small number of embryos were fertilised.

Experience of foreign specialists

Professor Alan Handyside from the United Kingdom played a major role in the development of the PGD method and its introduction into clinical practice in the early 1990s. The first PGD pregnancy in Central Europe was achieved in the Czech Republic in 2001.

On the occasion of the 25th anniversary of PGD, Professor Handyside has summarised the results to date.

It follows that this method has a really big impact on the success rate (more than 50%).