C/ Manuel de Falla, 6-8. 28036 - Madrid (España) Tel. +(34) 914 585 804 - Fax +(34) 914 571 756
Preimplantation genetic diagnosis (PGD) allows us to study embryos before being transferred to the uterus to see if the embryos are healthy or if they are carriers of a genetic disease. Only healthy embryos are then transferred to the patient.
The Human Genome Project has greatly helped us in understanding the exact molecular basis of many hereditary diseases. It has greatly helped the field of Assisted Reproduction by aiding the development of a technique that allows us to genetically diagnose embryos before implanting them into the uterus.
PGD is indicated in couples that are:
- Carriers of genetic anomalies such as chromosome reorganizations, numeric alterations or mosaic alterations in the karyotype.
- Couples who have had a pregnancy with a chromosome alteration.
- Carriers or people with monogenic diseases or diseases linked to the sex chromosomes.
- Women who have had more than two miscarriages or unsuccessful attempts at IVF cycles.
What are the techniques used in this study?
Fluorescence in situ hybridization (FISH) on the fixed nuclei of biopsied cells with target-specific DNA probes is the technique of choice to detect chromosome imbalance associated with chromosome rearrangements. It can also be used when it is necessary to select female embryos in families with X-linked disease for which there is no mutation-specific test. FISH has also been used to screen embryos for sporadic chromosome aneuploidy (also known as PGS or PGD-AS) in order to try and improve the efficiency of Assisted Reproduction. A genetic study is carried out on the 24 pairs of chromosomes while the embryos are kept in the incubator where they continue to develop to blastocyst. When the FISH results are reported, only healthy embryos are transferred.
This is a molecular technique that studies the 24 sets of chromosomes in different locations on the chromosome. It enables us to determine the numerical diseases in the embryo’s chromosomes and consequently which healthy embryos to use in transfer. Our clinic is working hard in this area so that in the future, all these diseases can be diagnosed.