Preimplantation Genetic Diagnosis
Preimplantation Genetic Diagnosis (PGD) is a highly advanced scientific technique to test and diagnose embryos for specific genetic or chromosomal abnormalities. We can then select the embryos that are not affected with the condition being tested for, before implantation to maximise the chance of a successful pregnancy.
Couples who may consider Preimplantation Genetic Diagnosis include:
- those who are at risk of having a child with an inherited genetic condition
- people who have had recurrent miscarriage
- those having had repeated embryo transfers without pregnancy
- those where one is known to have a chromosome rearrangement
- 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)
- couples who would find it difficult to consider termination of an affected pregnancy
Hunter IVF provides Preimplantation Genetic Diagnosis (PGD) and Advanced Embryo Selection (AES) through our broader IVFAustralia network.
What's involved in PGD?
In PGD genetic testing, 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, this means only those embryos diagnosed as being unaffected or free of a specific disorder will be transferred to a woman.
Advanced Embryo Selection
A new and more advanced form of Preimplantation genetic diagnosis, Advanced Embryo Selection, screens all the chromosomes in a developing embryo (previously only 8 to 10 chromosomes could be tested), enabling selection of the embryo with the greatest likelihood of pregnancy success.
This is a breakthrough in PGD technology as it is the world's fastest and most precise embryo selection test. It provides overnight results so your IVF treatment can continue uninterrupted, ensuring a fresh embryo transfer.
If you are undergoing IVF treatment, you may wish to consider Advanced Embryo Selection if you:
- Are over 38
- Have a history of miscarriage
- Have experienced repeated unsuccessful IVF
- Have hereditary chromosomal conditions.
- Find out more about miscarriage
Contact us for more information about genetic testing.
Other forms of PGD testing
Some people experience recurrent miscarriage which may be caused by a balanced translocation. This is where a part of one chromosome attaches to the end of another, or pieces of chromosomes may break off and be swapped around so although a person has a normal complement of chromosomes their children could inherit missing or extra pieces of chromosome.
We can use PGD to detect unbalanced translocations in an embryo and select embryos without the translocation to improve chance of pregnancy.
PGD can also be used to determine the gender of embryos, which is helpful as 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 identify the gender so only embryos of the unaffected gender and with the correct number of chromosomes will be transferred.
Gender selection is prohibited for anything other than medical reasons.
Single Gene Defects
A gene is a sequence of genetic material (DNA) with a particular function on a chromosome. 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 a 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.
If you have a parent who has been affected by a serious genetic condition such as Huntingtons disease later in life you may wonder whether this is a condition you can pass on to your children. 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.