24-Chromosome Pre-Implantation Genetic Screening (PGS)

Pre-Implantation Genetic Screening (PGS) allows for the screening of embryos during In Vitro Fertilisation (IVF) in order to identify abnormalities in the chromosomes caused by aneuploidy . Viafet's Exact Comprehensive Chromosomal Screening, ExactCCS, screens all 24 chromosomes for aneuploidy, increasing your chances of achieving a healthy pregnancy and decreasing your risk of miscarriage by identifying embryos with the healthy number of chromosomes. With over 15 years of experience in Reproductive Genetics, during which over 15,000 samples have been tested, Viafet specialized in PGS.

Is ExactCCS™ right for me?

Couples with a variety of medical histories have become pregnant following Viafet's 24-chromosome ExactCCS™. Studies show that PGS may be most beneficial for couples meeting one of the following criteria:

Couples have also chosen to complete 24-chromosome ExactCCS™ in the following circumstances:

  • Improve IVF success rate and reduce risk towards miscarriage: Aneuploidy is the leading cause of over 60% of IVF failures and pregnancy loss.
  • Male Factor Infertility: Male infertility factors, such as low quality sperm, have been linked with an increased rate of aneuploidy .
  • Concern for Down syndrome: In cases of a previous pregnancy involving aneuploidy or to reduce the risk of Down syndrome.
  • Interest in Gender Selection or concern for a sex-linked gender illness (if this service is offered by your healthcare provider).

Based on your medical history and personal preference, Viafet advises you to consult with your physician in order to determine if completing genetic testing such as ExactCCS™ is right for you. For more information on ExactCCS™, to discuss any questions related to genetic testing, or to learn where you may complete an IVF cycle with Viafet testing, contact Viafet today.

Additional Information

Maternal age of 35 years or older:

As a woman ages, the quality of her eggs and her ovarian reserve diminish while the reproductive organs maintain their ability to carry a pregnancy. Several studies have shown that women of advanced maternal age are at an increased risk of producing aneuploid eggs and of spontaneous abortion, making maternal age of 35 years and older one of the most common indications for completing genetic testing such as ExactCCS™

Repeated IVF Failure:

Repeated IVF failure is defined as the absence of an ongoing pregnancy after 3 or more embryo transfers with high quality embryos. One of the leading contributing factor for repeated IVF failure is the development of aneuploid embryos. Studies show that at least 15% of couples with repeated IVF failure have an increased frequency of aneuploid embryos, a rate that substantially increases with maternal age.

History of Recurrent Pregnancy Loss:

In more than half of recurrent miscarriage cases, the diagnosis is unexplained infertility. Several scientific studies have verified that 80% of unexplained recurrent pregnancy loss in women over the age of 35 can be explained by aneuploid embryos. In every study completed using genetic screening services such as ExactCCS™, a decrease in the miscarriage rate was observed. Before choosing 24-chromosome ExactCCS™, couples that have had two or more miscarriages should consult with their physician about having their own chromosomes tested to rule out inherited chromosomal rearrangements called translocations and inversions . For more information on Pre-Implantation Genetic Diagnosis testing for Inversions and Translocation, read about Inversion/Translocation PGD and 24-chromosome aneuploidy screening with ExactCCSPLUS™.

How does ExactCCS™ work?


Completing genetic testing during your IVF cycle provides a wealth of information about each embryo before being transferred to your uterus during Embryo Transfer. During an IVF cycle, 24-chromosome ExactCCS™ can be performed on day 3, 4 or 5 after Egg Retrieval by removing a single cell or cells from the developing embryo. Results are available 12-hours after receiving the samples. Viafet's fast reporting time allows for embryos to be transferred fresh or frozen, depending on your IVF physician's protocol.


ExactCCS™ is performed by array-CGH, a method that amplifies (magnifies) and compares the amount of DNA present for all 24 chromosomes (1-22, X and Y) to that of a healthy standard, detecting monosomies (missing chromosomes), trisomies (extra chromosomes) and other abnormalities. In 2004, the founder of Viafet Genomics Laboratory, Dr. Ali Hellani, established a new method of DNA amplification that improved the quantity and quality of resultant DNA from one embryonic cell. Today, after being adopted as the array-CGH protocol of Agilent Technologies, Dr. Hellani's protocol is utilized by scientists worldwide completing PGS through array-CGH. Results obtained through Viafet's Microarray testing are >99% accurate.

To learn more about benefits of Viafet's 24-chromosome PGS, watch the video below.

As of January 2015, Viafet also performs 24-chromosome aneuploidy screening by Next Generation Sequencing .

What is Aneuploidy?


Our bodies are made up of cells containing chromosomes . Each chromosome holds genes that code for the proteins essential for healthy development. In humans, each cell normally has 46 chromosomes. These 46 chromosomes are made of up 22 pairs, one pair from each parent, and the sex chromosomes, X and Y (XX in females and XY in males), making a total of 24 unique chromosomes. For this reason, genetic testing such as ExactCCS™ is referred to as 24-chromosome screening.

Aneuploidy, what does it mean and how does it happen?

When an individual has more or less than 46 chromosomes, they are said to have a chromosomal abnormality due to aneuploidy , additional or missing chromosomes. Having an extra chromosome, 47 instead of 46, is known as a "trisomy", while having a missing chromosome, 45 instead of 46, is known as a "monosomy".

Aneuploidy can naturally occur either when the egg and sperm cells are being made or as cells multiply and divide during early embryo development and are not necessarily associated with family history. However, the likelihood of aneuploidy occurring in embryos increases with maternal age as ovarian reserve quality diminishes.

Aneuploidy and pregnancy

Most aneuploid embryos either do not implant or result in early pregnancy loss -- over 60% of pregnancy loss or IVF failure can be attributed to aneuploidy. However, some chromosomal abnormalities have a higher occurrence in developing foetuses and can result with a baby being born with an abnormal number of chromosomes. These include:

  • Trisomy 21 (Down syndrome)
  • Trisomy 18 (Edward syndrome)
  • Trisomy 13 (Patau syndrome)

Aneuploidy can also occur in the sex chromosomes, X and Y. These include:

  • Klinefelter syndrome (XXY)
  • Turner syndrome (X)
  • Triple X syndrome (XXX)
  • Jacob syndrome (XYY)

Viafet's 24-chromosome ExactCCS™ can detect all of the conditions mentioned above. In some instances, there are not entire additional or missing chromosomes but rather small portions of chromosomes called duplications and deletions. Viafet's ExactCCS™ is able to detect duplications and deletions down to 5MBase.

Where can I get testing?

Talk to your IVF physician about 24-chromosome PGS and if it right for you. If your physician does not yet offer Viafet testing, please suggest that they contact us - testing can get started immediately. If your physician is already offering Viafet testing, all coordination for your case will be completed between your IVF centre and Viafet's team.

With locations in the United Arab Emirates (Dubai and Abu Dhabi), Australia, the Kingdom of Saudi Arabia, Lebanon and more locations coming soon, Viafet's services are available to a wide network of clinicians and patients. If at any time during your journey you have questions or would like to speak with a Genetic Counselor, contact Viafet and we will schedule an appointment immediately.