Genetic mutations, small errors in the DNA inside our bodies cells, can be the cause of a wide variety of disease. Common examples include Cystic Fibrosis or Muscular Dystrophy. If a person carries such a genetic mutation and is considering starting a family, they may wish to avoid passing this genetic trait on to their child.
Before PGD can be performed embryos are created in the IVF lab and grown for 5 to 6 days until they reach the blastocyst stage.
A specialized laser is used to make a small hole in the embryo's shell so that it may begin to 'hatch' and a very fine glass pipette is used to take a small sample of cells from the portion of the embryo that will become the placenta. This process is called embryo biosy.
Sensitive genetic techniques are then used to determine whether the embryo contains the mutation being tested for. Depending on the mutation being tested for it may be necessary to develop a specific test for your particular case, this may take some time and require genetic samples from several family members.
The principal benefit of undertaking PGD is to reduce the risk of a child being affected by the condition in question. For many couples this technique also allows them to avoid the difficult situation of discovering a fetus is affected during prenatal testing once a pregnancy is already established.
It is important to understand that PGD cannot 'fix' any embryos found to carry the mutation, it can only identify them.
As with every embryo handling procedure there is a potential risk of harm to the embryo.
We are only testing a small sample of the embryo and it is possible that these cells may not be the same as the rest of the embryos, something called Embryo Mosaicism. This can result in a false or unclear test result.
The very small sample we are working with and the variable nature of human embryos also means that we may not be able to obtain a result for some embryos. Even where a result is obtained, the limitations of working with such a small sample mean that testing is not 100% accurate and we strongly recommend confirmatory prenatal testing be performed.
If you are considering undertaking PGD speak with your fertility specialist to discuss whether this technique may be of benefit to you.
A genetic counselor is available and will conduct and appointment with all patients undertaking PGD to discuss these processes in more detail in regard to your specific situation.