This is an advanced technique first developed in the early 1990s. It is used to detect genetic disease and chromosomal disorders in embryos created through in vitro fertilisation (IVF). Up to 60% of early miscarriages are due to chromosomal abnormalities.
Currently there are various types of PGD available depending on the needs of each couple. PGD essentially involves the collection and genetic analysis of early-stage embryos (approximately three-days old). Healthy embryos with normal genetic and chromosomal structure are selected and transferred into the uterus for implantation. PGD does not involve manipulation of the genetic material in the embryos but rather it allows selection between them.
PGD testing is able to detect the most known genetic mutations. It is widely used by couples who are at risk of having a child with a serious genetic disorder, including chromosomal diseases such as Down’s Syndrome and other genetic disorders such as cystic fibrosis, sickle cell disease, Tay-Sachs disease, Huntington’s Chorea and spinal muscular atrophy.
At Life Clinic we promote the day five blastocyst biopsy, and the freezing of the embryos after the biopsy. With the arrival of the results we will be ready to transfer a chromosomally correct embryo that will have the highest chances for success.
The basic reason we are promoting the day 5 blastocyst is because the embryo at that point has already a large number of cells, and is less likely to be harmed by the biopsy, when we remove some cells for the testing.
Pre-implantation Genetic Screening (PGS)
This is variant of PGD which is also provided at Life Clinic. It is used specifically to detect aneuploidy, a chromosomal disorder. Perhaps the most known form of this is Down’s Syndrome where an extra chromosome is present. The combination of PGS with NGS can check a variety of chromosomal abnormalities as the chromosomal integrity of the embryo and the gender.
Fluorescent in-situ hybridisation (FISH) analysis
This is a relatively recent technology which is used in the laboratory to determine whether the correct number of certain chromosomes is present in the egg or embryo. The chromosomes most commonly associated with abnormalities during pregnancy are analysed. These are chromosomes 13, 16, 18 and 22. Fluorescent signals bind to these chromosomes enabling their number to be established. FISH has a published accuracy rate of 95%. However, it is important to realise that in some cases this analysis may reveal that no normal embryos are available for transfer or that the chances of being able to store excess embryos from an egg collection may be reduced.