Genetic Testing Of Embryos (PGS/PGD)

Genetic Screening Of Embryos (PGD/PGS)

What is the Genetic Screening Of Embryos?

Over the years, embryo selection has become more important than ever as several studies have shown that as much as 50% of embryos have chromosomal abnormality above the age of 37 years and are likely to fail if implanted into the uterus. 

With the help of the PGS technique, we can perform an embryo screening for any genetic or chromosomal abnormality before the transfer of the embryos. 

These new methods and techniques allow us to select high-quality embryos for transfer thereby reducing the risk of implantation and pregnancy failure. The most common techniques for genetic screening of embryos is PGT or Preimplantation Genetic Testing. 

What is PGS?

PGS also is known as PGT, is a screening of chromosomes for aneuploidy. It is used for screening for aneuploidies in embryos. Aneuploidy stands for an abnormal number of chromosomes. The term PGS most often comes in use while discussing infertility with couples who are struggling with issues involving age, repeated IVF failure, recurrent miscarriages, and genetically abnormal pregnancies. 

PGS is primarily used for the detection of chromosomally abnormal embryos. The most common technique for PGS is (NGS) Next-Generation Sequencing. This test screens for chromosome syndromes like Down’s Syndrome or Trisomy 21, Trisomy 13, and other chromosomal structural changes. 

Indications for PGS testing-

• Repeated IVF failure
• Recurrent miscarriages
• Severe male infertility
• Genetically abnormal pregnancies

Process of PGS-

The procedure is done in three steps. First, the embryos are produced using IVF or ICSI, fertilized embryos are then cultured for 3-5 days. After 3-5 days, embryo biopsy takes place. 2 or more cells are removed after every 3 or 5 days of biopsy for testing. After the cell is biopsied, are placed in test tubes and are sent for further testing. Till then the embryo is frozen and after the test, the embryo is finally transferred into the uterus.

What is PGD?

PGD is a screening method that allows us to test the embryos of those couples who carry a known risk of genetically inherited disorders. With the help of this screening method, only the healthy embryos are selected to replace or transfer to the woman’s uterus to achieve pregnancy. 

PGD has been very successful in detecting any kind of genetic alterations in the embryos of those who are known to be at risk of passing it on to their offspring. This test helps to identify chromosomally normal embryos for transfer that helps to improve the success rate of IVF. 

This test is especially good for those women who have a history of miscarriage, failed IVF cycles, and are old in maternal age. 

PGD is performed with the help of a high-powered microscope. One or more cells from the embryo are tested for the genetic train of interest. After this, the unaffected embryos are identified, separated, and transferred into the uterus. 

Indications for PGD Testing-

• Abnormal embryos
• Heredity Genetic abnormalities
• Increased risk of chromosome abnormalities
• Severe miscarriage
• Chromosome defect before pregnancy

Process of PGD-

The embryos are first created in a laboratory and are left for 5-6 days for growing. After 5-6 days, a biopsy is done on developing embryos. The embryos are then stored while genetic abnormalities are tested. After all this, the best embryo is selected and then transferred to the uterus.

What is the difference between PGD and PGS?

PGD diagnoses the embryo for a single gene disorder whereas PGS screens embryos for ANEUPLOIDIES and detects chromosomally abnormal embryos.

What are the benefits of PGD and PGS?

• PGD helps couples to pursue biological children which they wouldn’t be able to pursue otherwise
• PGD reduces the risk of conceiving a child with a genetic factor 
• PGD can reduce the need for amniocentesis later in pregnancy