What is PGD and when is it done?

PGD or Pre-implantation genetic diagnosis is a form of genetic testing exercised on the embryo cells produced during an IVF treatment cycle to know the genetic profile of the embryos. It is helpful in selecting the best embryos for pregnancy. Preimplantation genetic diagnosis (PGD) refers specifically to when one or both genetic parents has a known genetic abnormality and testing is performed on an embryo to determine if it also carries a genetic abnormality.

Who Should Get Pre-Implantation Genetic Diagnosis Done?

Preimplantation genetic diagnosis (PGD) is recommended when couples are at risk of transmitting a known genetic abnormality to their children. Only healthy and normal embryos are transferred into the mother's uterus, thus diminishing the risk of inheriting a genetic abnormality and late pregnancy termination (after positive prenatal diagnosis).

PGD should be offered for 3 major groups of disease:

(1) sex-linked disorders

(2) single gene defects

(3) chromosomal disorders.

Through a PGD test, the doctors can identify which embryos carry the genetic disorders and which doesnt. With the help of this test, it makes it possible for the doctors to transfer the best possible embryo into the uterus to try for pregnancy.

When is PGD Done in an IVF Cycle?

After the embryos are grown for five or six days, all the developing embryos undergo a biopsy through PGD. The genetic material found in the cells from the embryos is tested for abnormalities. After considering many markers in the embryos tested, the medical and genetics team will decide the best possible embryo that can be taken forward for implantation.

The Benefits of PGD

Currently available technology can help eliminate some genetic diseases in the future (eg, Tay-Sachs disease, cystic fibrosis, Huntington disease, X-linked dystrophies). Complete cures for many genetic diseases are not likely to be found soon; therefore, preventing the disease is preferable to waiting for a possible cure to eventually become available.

Doing screening for genetic diseases prior to implantation will prevent termination of pregnancy following prenatal testing(chorionic villous testing, amniocentesis) which can be a difficult and traumatic decision to follow through with.

In the past, persons with a genetic disease or those who know that they are carriers frequently choose not to have children in order to avoid the risk of passing on the disease to future generations. Now, PGD allows these couples the opportunity to have a child free of their particular disease.

Major Genetic Diseases That Can Be Screened Using PGD

One of the most significant uses for PGD is to identify and rule out embryos causing genetic disorders in the pre-implantation stage itself. Some of these diseases include: