Preimplantation genetic testing (PGT) is a technique in which a sample of the cells of the embryo are removed and the genetic composition of the embryo determined by complex gene analysis called next generation sequencing.
Who gets PGT?
PGT is often performed in couples who are at risk of having embryos with a chromosomal imbalance or genetic abnormality which may lead to disease. This may be because of their individual genetic makeup, their age or their past history.
What are the risks?
PGT is a new technology and data on the long term health of the children is not known. Preliminary data of the children is however reassuring. There is a small risk that the embryo may not survive the biopsy.
As with any diagnostic test, errors can occur but these are uncommon. Sometimes the genetic code cannot reliably be analysed and the biopsy is indeterminate.
What is the process?
- Biopsy is often performed on Day 5 and both embryos and biopsy are then frozen. Sometimes embryos do not develop until Day 5 and this particularly occurs when only a few eggs can be collected from the female.
- Biopsies are kept until they can be analysed as a group as this keeps the costs of the analysis as low as possible.
- When we get the biopsy results the uterus of the woman is prepared for embryo transfer and the normal embryo is transferred to the uterus. Not all normal embryos will result in the establishment of a pregnancy. This could be because the process of warming the embryo, the uterine environment and other factors which are as yet unknown. Pregnancy rates from embryos that have been screened genetically is generally higher than embryos which have not been screened.
Sometimes it is difficult to determine the best embryo to transfer and this is discussed with your doctor when the results are available.
Using PGT to select for gender except when serious medical conditions may be transmitted is not allowed in Australia.