Infertility – Genetic diagnosis

All Patients starting the IVF procedure are strictly recommended to perform all tests belonging to the basic panel of genetic tests. Based on the obtained results, physicians will be able to estimate the potential risks of transferring a disease to offspring or the occurrence of genetic defects. On this basis they will be able to suggest the appropriate medical procedures in order to increase the probability of successful IVF procedure and of giving birth to a healthy baby.

Most often the Patients are recommended to perform the following tests:

KARYOTYPE

Karyotype is the complete set of 23 pairs of chromosomes, which is present in the cells of every human body containing the comprehensive genetic information. The karyotype testing consists in the evaluation and description of the number and structure of chromosomes in a given individual. It allows to detect potential abnormalities – in healthy people primarily in the chromosomal structure. Disorders of this type (the so-called translocations) usually cause no symptoms in an adult “carrier” but hey can contribute to the occurrence of genetic defects in her or his children. The karyotype test should be performed in both partners. It makes it possible to estimate the potential genetic risks in a given couple (especially if it has a positive genetic history or has experienced miscarriages or reproductive failures).

AZF

This tests allows to detect microdeletions in the AZF (azoospermia factor) regions located on the long arm of the Y chromosome (it is not possible to detect them with the use of cytogenetic techniques) and to determine whether the male infertility has a genetic background.

In the AZF region of the Y chromosome, genes coding proteins involved in spermatogenesis, i.e. the process of sperm creation, are found. The presence of microdeletions in the AZF region of the Y chromosome causes dysfunctions of proteins responsible for the proper production of male gametes and is one of the genetic factors of development of male infertility. It is considered that approximately 25% men with infertility disorders have microdeletions in the AZF regions of the Y chromosome. Mutations (deletions) in AZF regions are the cause of reduced semen parameters, i.e. the so-called azoospermia or severe oligospermia, meaning – respectively – the absence or very low number of sperm cells in semen. Changes within the AZF gene are inherited in the male line.

CFTR

The test consists in the basic analysis of mutations in the CFTR gene. It covers two mutations most common in the Polish population – delF508 and dele 2,3 – which account for approx. 60% of all mutations. Mutations in the CFTR gene are the cause of the development of cystic fibrosis. The CFTR gene is located on chromosome 7 and it encodes a protein in cell membranes which forms the chloride ion channel.

Cystic fibrosis is one of the most common genetic diseases with an autosomal recessive pattern of inheritance. In the Polish population it occurs in 1 per 2500 births. The broad spectrum of cystic fibrosis symptoms is caused by the production of secretion of increased viscosity in all body organs with mucous glands. This results in alterations mainly in the respiratory, gastrointestinal and reproductive systems. Changes in the reproductive system lead to bilateral absence or obstruction of vasa deferentia in men (CAVD – Congenital Absence of the Vas Deferens), and the increased density of cervical mucus in women, inhibiting the sperm migration. It is estimated that 1.5 million individuals in Poland are asymptomatic carriers of mutations in the CFTR gene. For these reasons, a positive result of the CFTR test in one of partners is the indication for performing this test in the other partner. The diagnosis of the presence of the disease-carrying gene in a couple allows to predict the risk of giving birth to a sick child.

FACTOR V LEIDEN

This test consists in detecting the presence of G1619A mutation in the gene of factor V of the blood coagulation system – proaccelerin.

Factor V is one of proteins taking part in the blood coagulation process. A mutation of Factor V called Leiden mutation, inherited in an autosomal dominant manner, is one of the most common genetic causes of the development of thromboembolic diseases. This mutation is also the cause of the increased risk of spontaneous abortions, as well as other pathologies of pregnancy (third-trimester intrauterine foetal death).

TEST FOR MUTATION IN THE PROTHROMBIN GENE

This test consists in detecting the presence of G20210A mutation in the gene of factor II of the blood coagulation system – prothrombin. The presence of 20210G>A in the prothrombin gene is associated with the increased risk of the development of a thromboembolic disease, spontaneous abortions and other pathologies of pregnancy (intrauterine foetal deaths).