Preimplantation Genetic Diagnosis
Preimplantation Genetic Diagnosis (PGD) is a highly sophisticated scientific technique to test embryos for specific genetic or chromosomal abnormalities. It allows us to select embryos that are not affected with the condition being tested for, prior to implantation and pregnancy.
Melbourne IVF offers an internationally recognised PGD program and is a leader in the development of PGD testing in Australia. The program has helped hundreds of couples conceive healthy babies, many after long periods of infertility or with serious genetic diseases in the family.
Couples who may wish to consider Preimplantation Genetic Diagnosis include:
- those who are at risk of having a child with an inherited genetic condition
- those where one is known to have a chromosome rearrangement commonly referred to as a translocation
- anyone having a previous chromosomal abnormality in a pregnancy
- when the female partner is older (usually to test for Down syndrome where the female partner is over 38 years old)
- people having recurrent miscarriage
- those having had repeated embryo transfers without pregnancy
- couples who would find it difficult to consider termination of an affected pregnancy
What does PGD involve?
In PGD, one or two cells are removed from a day-3 embryo and tested for conditions such as cystic fibrosis or Down syndrome. Used with IVF, it means only those embryos diagnosed as being unaffected or free of a specific disorder will be transferred, maximising the chance of a healthy baby.
Advanced Embryo Selection
Advanced Embryo Selection is a new and more advanced form of PGD testing, that allows all 23 pairs of chromosomes in a developing embryo to be tested (previously only 8 to 10 chromosomes could be tested). This allows us to precisely select the embryo with the greatest likelihood of pregnancy success. And because results are available in 24 hours, you can undergo a fresh embryo transfer allowing your IVF treatment to continue uninterrupted.
This major innovation is particularly suited for couples where:
- the female partner is over 38 years
- they have a history of miscarriage
- they have experienced repeated unsuccessful IVF attempts
- either partner has an hereditary chromosomal condition.
Advanced Embryo Selection is exclusively available in Victoria through Melbourne IVF.
Other forms of PGD testing
Testing for a translocation
In some people, part of one chromosome attaches to the end of another, or pieces of chromosomes may break off and be swapped around so although that person has a normal complement of chromosomes their children could inherit missing or extra pieces of chromosome. This is known as ‘unbalanced translocation’.
Embryos with unbalanced translocations usually do not implant, miscarry, or rarely are born with severe abnormalities. We can use PGD to detect unbalanced translocations as well as errors of all other chromosomes in an embryo.
Gender Selection
Some genetic conditions affect one gender, for example haemophilia and muscular dystrophy. Sometimes it is not possible to detect the exact genetic error that causes the disease, but PGD can be used to determine the gender of embryos, as well as errors of all other chromosomes, and only embryos of the required gender and with the correct number of chromosomes will be transferred. Gender selection is prohibited in Victoria for anything other than medical reasons such as for family balancing.
Single Gene Defects
A gene is a sequence of DNA (genetic material) on a chromosome with a particular function (humans have up to 20,000 different genes, arranged on 23 pairs of chromosomes). When the DNA sequence on a particular gene is altered, a genetic disorder, such as cystic fibrosis, may result.
To identify which embryos are unaffected by the single gene defect that is present in the family, a patient-specific test is developed by the PGD team. As these tests are couple-specific, they can take some time and effort to design and establish.
Exclusion testing
Some people have (or have had) a parent affected by a serious genetic condition, such as Huntingtons disease, that does not generally manifest until later in life. Many people do not want to have testing to determine if they have inherited that condition from their parent, but at the same time do not want to risk passing it on to their own children.
In this situation PGD can be used to perform exclusion testing. In exclusion testing, the genetic error itself is not tested for, but embryos are tested to make sure they have not inherited the ‘at risk’ gene from the member of the family who has the condition.
> Find out more about chromosomal abnormalities
> Find out more about miscarriage
> Contact us for more information about genetic testing
