What are aneuploidies?

Pre-implantation diagnosis of embryos is most commonly used to prevent severe congenital genetic diseases from occurring in the offspring.Chromosomal abnormalities of embryos are one of the main causes of IVF treatment failure. Each embryo cell should contain 23 pairs of chromosomes, i.e. 46 in total.They are the carrier of genetic information and allow the embryo to develop properly. Aneuploidy is the presence of an abnormal number of chromosomes in a cell (e.g. 45 or 47 chromosomes). An extra or missing chromosome is a common cause of some genetic disorders. Most cases of aneuploidy result in miscarriage or the embryo does not implant at all. In other cases, a child may be born with a genetic disorder.

CAG

PGD testing of the embryo is performed in patients who are known to have a genetic burden. Especially in those who are carriers of monogenic diseases that they can pass on to their offspring, such as cystic fibrosis. Other indications for testing include: genetic diseases in the family, carriage of chromosomal translocations, previous miscarriages of unknown cause, previous failures with IVF. Thanks to diagnostics, the risk of transmission of genetic diseases to the child can be eliminated and genetic diseases that arise accidentally can be detected. This will protect the couple from a possible difficult decision to terminate the pregnancy.

It is worthwhile for couples with genetic disorders who qualify for PGD to undergo appropriate genetic counselling. In many cases, this may be the only chance of having healthy offspring. If the test reveals an abnormality, doctors will recommend that the couple use sperm or ova from young and perfectly healthy donors.

PGS

Patients who do not have a genetic disease are tested, but whose attempts to get pregnant fail, such as recurrent miscarriages or unsuccessful embryo implantation during an IVF procedure. Also, very poor semen quality can be a reason to have the test done. The PGS test is called screening - it helps to determine the root cause of the problems and to detect possible abnormalities in the number of chromosomes. Likewise, a donor age of over 38 years can be a basis for PGS testing.

You should think about testing embryos when:

You have already had several miscarriages due to genetic diseases,
have undergone several unsuccessful attempts at IVF,
Semen is of very poor quality,
you already have a child with a genetic disease,
you know that someone in your family has a genetic load,
previous studies have shown chromosome abnormalities,
know that you are a carrier of diseases such as cystic fibrosis, sickle cell anaemia and Tay Sachs disease, achondroplasia, Huntington's disease.

What does the PGS study look like?

The test is performed to detect abnormalities in the number or structure of an embryo's chromosomes before it is implanted in the uterus. It involves the collection of blastomeres during the IVF procedure, usually on the fifth day after fusion with the sperm. By then it is already divided into several dozen cells (blastomeres). A laser is used to make a small hole in the casing through which the material will be taken for diagnosis. Once the biopsy is complete, the embryo is placed in an incubator and the cells are analysed using next-generation sequencing (NGS). The technique makes it possible to distinguish between normal and abnormal cells. If the embryo does not show abnormalities, it can be placed in the aspiring mother's uterus. This increases the chance of pregnancy and also reduces the risk of miscarriage and of diseases caused by aneuploidy, i.e. Down syndrome, Edwards syndrome or Patau syndrome.

To find out what the couple's genetic testing, including PGD and PGS, looks like go to here.