Genetic diagnosis – what is it?
Before answering this question, we need to understand what genetic diagnosis is and when and how it is performed.
Preimplantation genetic diagnosis (PGD) is a molecular genetic study that allows us to detect the presence of genetic disorders, random mutations, and hereditary diseases in the embryo. This procedure is technically possible only with in vitro fertilization. If fertilization has not been carried out in the same way, it is not possible to make a genetic diagnosis.
The procedure involves the biopsy of one or less than two cells from a dividing embryo. The obtained cells are then examined using one of the following methods:
- FISH – fluorescent in situ hybridization;
- Comparative genomic hybridization on microarrays;
- polymerase chain reaction (PCR).
The methods are not interchangeable and are not universal: most of them can detect only a certain group of pathologies, but not all possible ones. Therefore, the choice of a particular research method is made only by a doctor, based on many factors: the presence of a burdened heredity in one of the parents, detected genetic disorders, suspicion of a mutation in a particular part of the embryo genome, and so on.
The procedure is complicated and requires considerable knowledge on the part of the doctor. At the same time, parents can learn in advance about all possible genetic abnormalities of the future child, determine its gender, and the likelihood of a miscarriage. Thus, the procedure in general will be useful for most parents using in vitro fertilization.
Indications for PGD
Genetic diagnosis of the embryo of the unborn child is obligatory in the following cases.
- If one or both parents have chromosomal mutations (Tay-Sachs disease, cystic fibrosis, hemophilia A, Duchenne myodystrophy, sickle cell anemia, etc.).
- At high risk of occurrence of mutations not connected with hereditary diseases: the age of the mother over 35 years and the father over 39 years.
- In cases of spermatogenesis disorders in the father.
- In the case of recurrent miscarriage of unclear etiology.
In addition, genetic diagnosis is highly recommended after several unsuccessful in vitro fertilization attempts.
Results and risks of PGD
Only healthy embryos without pathological mutations are transferred into the uterus. A healthy baby is born.
The risk of miscarriage is halved.
The risk of multiple pregnancy, the main complication of IVF treatment, is halved.
Overall, the chances of a successful embryo implantation are increased by 10 percent and of a successful pregnancy and birth by 20 percent.
The only possible complication of genetic diagnosis is the accidental damage of the embryo, but the probability is less than 1 %. The probability of an error in which an embryo with genetic disorders can be accepted as healthy is no more than 3.5%.