Carrier screening and preimplantation genetic testing are optional tests that can give you more insight into your risks of encountering certain genetic conditions when building your family. The results of these analyses can guide treatment decisions, give you added peace of mind, or help you to prepare for the future. Genetic testing is not compulsory as part of your treatment but may be strongly recommended in certain situations.
Genetic reproductive carrier screening (RGCS) is a blood or saliva test used to identify whether you are a carrier of a specific genetic condition. Carriers are usually healthy themselves but can pass on the gene for a hereditary illness to their child. Depending on the specific combination of genes passed down by each parent, a child may end up being affected by the condition.
Your fertility specialist may recommend carrier screening whether you have a known family history of an inherited condition or not. This is because some of these genes can be passed down via carriers for generations without affecting anyone.
Various types of carrier screening tests are available. The 3-gene analysis tests for cystic fibrosis, spinal muscular atrophy, and fragile X syndrome, and attracts a Medicare rebate. Alternatively, you may want to consider expanded carrier screening, which looks for over 600 genetic disorders, most of them very rare. Expanded screening tests are not covered by Medicare.
PGT is often offered for couples or individuals undergoing IVF. This test is designed to analyse the genetic material of an embryo created through the IVF process, and can tell us whether there are any problematic genes that may result in a higher likelihood of an unsuccessful pregnancy or a child born with a genetic disorder.
Several cells are biopsied from each suitable embryo developed through IVF. Taking these cells does not harm the baby as they’re sampled from the layer that would go on to form the placenta. By testing each embryo, we are able to select only genetically normal embryos for implantation, improving your chances of a healthy baby.
Your fertility specialist may recommend you consider PGT if:
There are three types of PGT.
PGT-A: preimplantation genetic testing for aneuploidy is designed to look for an abnormal number of chromosomes. A normal embryo has 23 pairs of chromosomes. An embryo that has too many or too few chromosomes, known as an aneuploid embryo, will result in a child born with a genetic condition. Some of these conditions are not survivable. Examples of aneuploid conditions include Down syndrome and Turner syndrome.
PGT-M: preimplantation genetic testing for monogenic conditions assesses an embryo for a specific gene mutation. Typically, PGT-M is used when one or both parents are known to carry the mutation or are affected by the mutation. This increases the risk of passing on the faulty gene to your child. Examples of a monogenic condition include muscular dystrophy, cystic fibrosis, fragile X syndrome, and sickle cell anaemia.
PGT-SR: preimplantation genetic testing for structural rearrangements is offered when you and/or your partner are known to have a balanced chromosomal rearrangement. This means that you have the correct number of chromosomes but in a different arrangement. While this doesn’t affect your health, it does increase the risk of producing an embryo that has an abnormal amount of genetic material. Embryos affected by an unbalanced rearrangement will usually not survive to birth.
