Pre Implantation Genetic Diagnosis
What is PGD?
Pre Implantation Genetic Diagnosis is a prenatal diagnostic method performed on the embryos before they are transferred to the female’s uterus. It involves a genetic study on biopsied embryo cells to diagnose possible chromosome or genetic abnormalities. Following the study, only the healthy embryos are chosen for the embryo transfer.
PGD is a complex process and cannot be used to screen for all diseases/disorders. The law regulates which hereditary conditions can be screened for if present in the parents, as well as which ones cannot be screened for. Some conditions and diseases require us to apply for special permission from the Spanish National Commission on Human Reproduction.
The Pre Implantation Genetic Diagnosis Procedure
PGD is indicated when the embryos are at risk for serious abnormalities regarding the number or structure of chromosomes, a gene abnormality which could be the cause of an inherited genetic condition, or when there is reasonable doubt regarding embryo viability.
There are four phases involved in this treatment.
PHASE I: PRELIMINARY INFORMATION
In this phase we will perform genetic testing on the parents to screen for any conditions which could be passed down to offspring. The objective is to gather as much information as possible before carrying out PGD.
PHASE II: OBTAINING THE EMBRYOS
Once all of the necessary information has been collected, the embryos will be obtained by In Vitro Fertilisation, for added security, even if the parents don’t have any issues conceiving.
PHASE III: EMBRYO BIOPSY AND GENETIC ANALYSIS
The embryo biopsy can be performed at one of two possible stages:
1). On day 3 following fertilisation, when the pre embryo contains 6 8 cells, we remove one or two cells without compromising embryo development.
2) On day 5 or 6 following fertilisation, when the pre embryo has reached blastocyst stage, we remove several cells from the trophectoderm. In this case, the embryos must be frozen after the biopsy due to the amount of time required to obtain the results.
After the biopsy has been performed, the pre embryo will remain in the culture medium or will be frozen until the results of the diagnosis are ready and the possibility of an embryo transfer can be evaluated. The biopsy obtained is sent to a genetics laboratory of reference where it will be processed using Array CGH, PCR or Next-Generation Sequencing (NGS) techniques. We will receive an analysis and diagnosis for each embryo that was biopsied.
PHASE IV: EMBRYO TRANSFER
Once we have the results of the genetic analysis we will decide which embryos are going to be transferred based on genetic chromosomal make up and characteristics of embryo viability.