When should a genetic compatibility test be performed?
The GCT (genetic compatibility test) helps to reduce the transmission of genetic diseases to the offspring of a couple. Its objective is to identify the altered genes of each member of the couple and to detect any mutations in common. This test is capable of preventing the transmission of about 600 genetic diseases, many of which currently have no cure. That is its greatest importance: it prevents the birth of sick children.
Any couple can take this test to discover the mutations in their genetic material. This is a very interesting test, since in case of sharing a mutation with the couple, concrete actions can be taken if they decide to have offspring.
However, this test is usually requested in specific cases:
- Before an assisted reproduction treatment. If this study is performed, the most appropriate treatment for each couple can be recommended. It is essential to perform this test if any member of the couple already knows that he/she has a genetic disease.
- Before treatment with gamete donation. The genetic compatibility test makes it possible to select the sperm donor or the egg donor who does not share the same mutations with the recipient. Thus, the risk is much lower.
- Consanguineous couples. When the members of the couple have some kind of kinship, are from geographically isolated areas or from “closed” ethnic groups, it is highly recommended to perform this test.
What does it mean if we are both carriers of the same genetic mutation?
If both parents are carriers of the same genetic mutation, the risk of having a baby affected by this disease is 25%. If the Genetic Compatibility Test, on the other hand, does not detect any genetic mutation in common, the parents can be sure that their children will not inherit the recessive diseases included in the study.
What is a genetic compatibility test for?
In a recessive inherited genetic disease, both copies of a gene are altered, and that is when a disease manifests itself. This can occur when the patient has inherited 2 defective copies of the gene, one from the father and one from the mother. The parents may be healthy carriers of the pathology; they would not have any symptoms, so they may never know that they have any mutated gene.
In fact, most of the population has genetic mutations that can be passed on to their offspring without knowing it. It is only when 2 people with the same genetic mutation come together that the disease can appear in the child they have.
If the parents have a common mutation, the probability that their offspring will inherit it is 25%. The probability of being only a carrier would be 50% and of being completely healthy, 25%.
For these reasons, there are many people who prefer to perform a PGD during the search for pregnancy.
Benefits of genetic compatibility testing
- Better embryo selection. The aim of PGD is to detect healthy embryos. In this way, embryos that may have mutations or aneuploidy are discarded. Without this analysis, they could be confused and transferred to the mother. This would lead to implantation failures, miscarriages or births of sick children.
- Lower risk of miscarriages. By not having the correct genetic endowment, weeks after the implantation of the embryo, an unexpected miscarriage could occur, since some chromosomal alterations would produce this implantation.
- Higher pregnancy rate. Thanks to PGD, embryos that may cause implantation failure are avoided.
- Fewer IVF treatments. The number of failed transfers would be reduced, since PGD chooses the embryo with the greatest implantation capacity and that can become a healthy baby. The time to achieve a pregnancy, therefore, is significantly reduced.
Greater peace of mind for patients. PGD eliminates the uncertainty as to whether or not the embryo would be healthy. In addition, the patient, knowing that everything is fine with the embryo, relaxes and the possibility of miscarriage is reduced.
How is the process to perform the Genetic Compatibility Test?
In order to perform this test, blood is drawn from each of the parents in order to analyze the DNA through different genetic techniques. Depending on these, the average time for the arrival of the results is about 30 days.
The purpose of this test is to analyze approximately 550 genes. Of these, up to 4,500 mutations linked to about 660 recessive genetic diseases can be detected. The most common are cystic fibrosis, spinal muscular atrophy, hemophilia, fragile X syndrome, or thalassemia, among others.
What happens if a genetic incompatibility is found in the couple?
As mentioned above, just because a person is a carrier of a recessive genetic disease does not mean that he or she will develop the disease. For this to happen, the 2 members of the couple have to have the same mutated gene in common. And even then, the chances of having a sick child are 25%; 25% that the child will be born healthy and 50% that the child, like its parents, will be a carrier of the gene.
If the aforementioned case occurs and the 2 members of the couple are carriers of the same disease, it is advisable to perform PGD (preimplantation genetic diagnosis) to select the embryo(s) free of the disease.
This test is also indicated for cases of ovodonation. If a carrier test is performed on the egg donor, it is best to perform the same test on the recipient couple. In this way it is ruled out that the egg or sperm are carriers.
