Preimplantation genetic testing (PGT) is an optional genetic test that you can consider when undergoing IVF fertility treatment. Though not every single possible genetic condition in existence can be covered in PGT, we are able to test for and exclude a significant number of inheritable diseases.
There are three different forms of preimplantation genetic testing offered at our Wollongong fertility clinic. The process for any type of PGT involves extracting several cells from the outer layer of an embryo created through IVF. This layer will later develop into the placenta, so no cells that will form your baby are disturbed. The cells can then be assessed for their genetic material.
Aneuploidy means a cell (or an embryo) has too few or too many chromosomes. The normal number is 23 pairs – 23 individual chromosomes from each parent. An abnormal number of chromosomes in a sperm or egg cell, which should have 23 each, is usually due to a problem during cell division.
Embryos with aneuploidy are often unable successfully to grow through the pregnancy, resulting in higher rates of miscarriage. For aneuploid embryos that do make it to a live birth, they will be affected by a chromosomal condition such as:
A monogenic condition is one that is caused by a single gene mutation. We consider PGT-M when you or your partner already know that you have a risk of passing on this gene, whether you have the actual condition yourself or not. People who carry the mutated gene without being affected by the condition are known as carriers. You may be aware of a family history of a genetic disorder, which means you have the potential to be a carrier.
PGT-M can be designed to test for any single-gene condition as long as we know what the condition is and which gene is involved. The most common disorders are:
A chromosomal structural rearrangement can include a translocation (when a section of one chromosome is stuck to a different chromosome) or an inversion (when part of a chromosome detaches and then reattaches in an abnormal orientation).
Though a balanced chromosomal structural rearrangement means you still have the right number of chromosomes yourself, it increases the risk of passing on an abnormal number of chromosomes via your eggs or sperm. If you are aware that you or your partner have a balanced structural rearrangement, you may want to consider PGT-SR testing. Unbalanced chromosome material is generally not compatible with life, and these embryos often are lost through miscarriage.
For all our patients who choose to take advantage of PGT, we provide genetic counselling. The results of a preimplantation genetic test can place you in a difficult ethical and moral situation, particularly if the results are positive for a genetic abnormality.
If the genetic abnormality is not compatible with life or you don’t feel you are in a position to care for a special needs baby, you can choose to discard the embryos.
If you and your partner are affected by recurrent miscarriages due to chromosomal abnormalities or have a known inheritable disorder that is identified during PGT, you still have options. The number of babies conceived through donor egg and sperm in Australia have been increasing over time, and provide a sensible option for parents who want to avoid the risk of passing on a genetic defect to their children.
