Preimplantation Genetic Testing

Detecting Chromosomal Disorders through Pre-Genetic Diagnosis

Pre-genetic diagnosis (PGD) is the use of genetic testing technology to assess and evaluate embryos for abnormalities. Also called preimplantation genetic diagnosis, PGD can be performed using many techniques available. In the in vitro fertilization (IVF) process, an egg is fertilized with sperm in the laboratory setting. After a few days, the resulting embryo is biopsied for genetic analysis. This allows the embryologist to evaluate if or not the embryos are genetically normal or if chromosomal abnormalities exist.

Why are embryos analyzed?

Fertility Clinic DubaiEmbryos are analyzed for one or more reasons. These include:

  • Gender selection – For family balancing, the embryologist can assess the embryo’s gender.
  • Aneuploidy – With this condition, there is an extra chromosome or a missing one. Down Syndrome is an example of aneuploidy, which is more common as a woman ages.
  • Translocations – This refers to a change in chromosome structure, where chromosomes are attached to each other, or where pieces of two different chromosomes are interchanged.
  • Recurrent pregnancy loss – Certain genetic defects can cause repeated pregnancy losses.
  • Single gene disorders – Diseases or conditions caused by an inherited single mutated gene. Examples include Sickle Cell Anemia, Cystic Fibrosis, and Tay Sachs.

The PGD Process

The pre-genetic diagnosis can be done using different approaches. These are:

  • Microarray method – This form of preimplantation genetic screening requires a blood test from the parents to create a DNA fingerprint. This can be used to compare the DNA from the assorted embryos to make sure there is one chromosome from each parent for every 23 pairs of chromosomes. This technique has the ability to test all chromosomes in less than two days. In addition, this test can be used to calculate the estimated accuracy of the result, which avoids errors.
  • Fluorescent in situ hybridization (FISH) – With this method, a single cell is analyzed under the microscope. Fragments of DNA are specified to each chromosome being tested using microscopic markers and fluorescent single detection.
  • Comparative genomic hybridization (CGH) – Also called a blastocyst biopsy, CGH tests the chromosomes expelled by the eggs during cells division after fertilization. This involves using cells of a day-5 embryo.

How accurate is PGD?

The accuracy of preimplantation genetic testing varies from couple to couple. There is a chance that PGD will not be 100% reliable. However, accuracy rates are 98% for most couples.

After the ResultsIVF treatment photo

Once PGD testing results are available, the fertility specialist discusses them with the clients, and only normal embryos will be used for IVF cycles. One or two embryos are placed in the woman’s uterus, and extra embryos are frozen for later cycles. PGD allows the doctor to use genetically normal embryos for transfer, increasing the chances of IVF success. When all chromosomes are evaluated, and assessed as normal, the chances of pregnancy is around 85-90%.

PGD for Failed IVF Treatment

When a couple experiences a failed IVF cycle, PGD is recommended. One of the most common reasons IVF fails is genetic abnormalities of the embryos. Women may have factors that cause their ovaries to produce genetically abnormal eggs, which produce problems with the embryos. This will lead to unsuccessful IVF treatment. Egg donors can be an option when this is found. If the male’s sperm contributes the abnormal genetic material, donor sperm may be used.

PRC Fertility Center is a top Dubai fertility clinic with over 25 successful years in America. Now open in Dubai Healthcare City, PRC has Board Certified providers with exceptional live birth success rates for IVF, ICSI, tubal reversal, and all aspects of Assisted Reproductive Techniques. Call us today!

Preimplantation Genetic Testing in Dubai

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.

PGD Clinics

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:

 

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