Preimplantation genetic testing, also called preimplantation genetic diagnosis (PGD), is a process of removing a cell from an embryo for genetic testing. This is done at PRC Dubai fertility center to assess for diseases and conditions that could interfere with the embryo’s survival once it is introduced into the uterus. PGD is used in the in vitro fertilization (IVF) process.
History of PGD
The first IVF procedure was completed in 1978. Years later, scientists began testing the embryo for potential health problems as well as chromosomal abnormalities. PGD was used in humans in 1990, and many improvements have occurred with PGD in the last 25 years. Genetic technologies used on cells removed from embryos and embryo biopsy have improved drastically over the last couple of decades.
Stages of Egg and Embryo Development
Three basic stages exist at which embryos or eggs may be biopsied to remove cells for testing. These include:
- Polar body – This is an early stage where the polar body of the egg is removed and tested. A mature human oocyte (egg) has one polar body, and a fertilized egg has two polar bodies. This technique does not alter the egg or embryo so that it cannot implant into the uterus or develop into a fetus. However, there is the chance of damage to the developing embryo with polar body biopsy.
- Cleavage stage – Day three of the embryo’s development is stage three. At this point, the embryo has 6-10 cells. Removal of the outer shell (zona pellucida) is performed so 1-2 cells can be removed for testing. Stage three development is important for the embryo’s development, so many IVF programs are not performing this technique.
- Blastocyst stage – The trophectoderm biopsy is the technique performed during the blastocyst stage of embryo development. After the embryo is formed into a multi-cell mass (trophectoderm), it has a fluid-filled cavity. This biopsy involves making a small hole in the shell of the embryo so several cells can be removed for testing.
The best fertility clinics for PGD are the ones with the best IVF success rates. The clinic should have an excellent culture system in order to obtain the maximum number of quality cells for biopsy. The clinic should also be skilled in embryo biopsy and blastocyst freezing, as well as successful in thawing frozen eggs and embryos.
Candidates for PGD
The most common reason for preimplantation genetic testing is advanced age. Women of advancing age have increased rates of chromosomally abnormal eggs, which develop into abnormal embryos. Five main types of clients should use PGD. These include clients who:
- Are having IVF with female age of 38 years or older
- Have repeated IVF failure, defined as three or more failed attempts
- Have a family history of inherited genetic diseases
- Are carriers of chromosomal translocations
- Have had recurrent miscarriages
Rates of Chromosomal Abnormality
The percentage of eggs with some type of chromosomal abnormality does increase as the woman ages. Approximately 45% of human embryos have some form of chromosomal abnormality. By testing the embryos available for transfer, we can avoid use of ones with abnormalities and choose healthy, high-quality embryos for transfer the woman’s uterus. PGD testing of early embryos will increase the chances of a successful pregnancy.
Technology used to Assess Chromosomes
There are three technologies currently being used for assessment of chromosomal abnormalities. These are:
- Array Comparative Genomic Hybridizaiton (aCGH)
- Quantitative Real-Time Polymerase Chain Reaction (qPCR)
- Single Nucleotide Polymorphism Microarrays (SNP)
PRC Dubai is the top fertility center in Dubai. After two successful decades of treatment at several metro Los Angeles fertility centers, PRC is now open in Dubai Healthcare City! Call us today at 800-4544.
Here is a video on PGD Testing: