Preimplantation genetic testing (PGT)

Preimplantation genetic testing for aneuploidy (PGT-A), (previously known as preimplantation genetic screening – PGS), is a genetic test that aims to identify embryos that are:

• Euploid: with the correct number of chromosomes
• Aneuploid: with missing or additional chromosomes
• Mosaic: with both euploid and aneuploid cells.

PGT-A may increase the chance of embryo implantation and reduce the likelihood of miscarriage or birth of a baby with a chromosomal abnormality. There is limited evidence of the effectiveness of PGT-A in general use. There is some evidence that use in older women may reduce miscarriages, though this has not been shown to increase the number of births.

PGT-A is an 'add-on' IVF procedure and will incur out of pocket costs over and above a routine cycle of fertility treatment.

Approval from the Reproductive Technology Council is required before performing PGT-A unless the woman providing the eggs:

• is greater than 35 years of age
• has experienced two or more miscarriages
• has experienced two or more failed IVF attempts after embryos transfer
  or
• has been referred by a geneticist and has a family history of aneuploidy.

Preimplantation genetic testing for monogenic disorders (PGT-M) is a genetic test that checks embryonic cells collected via in vitro fertilisation (IVF) to identify embryos with a specific genetic condition that affects a single gene. PGT-M may be used when the parents are known carriers of a genetic condition. In these cases, the embryos are tested for the specific mutations carried by the parents. Carrier embryos or embryos without the genetic mutation are then considered for transfer. PGT-M does not screen embryos for a panel of genetic conditions.

PGT-M may be appropriate when:

• a person is affected by a genetic condition
• a woman is a carrier of an X-linked condition
  or
• a person and their partner or donor are both carriers of the same genetic condition.

PGT-M may reduce the risk of miscarriage or the likelihood of the birth of a baby with the specific genetic condition.

Approval for PGT-M is required from the Reproductive Technology Council. Support from a clinical geneticist or genetic counsellor is required.

Preimplantation genetic testing for structural rearrangements (PGT-SR) is a genetic test that checks embryos collected via in vitro fertilisation (IVF) to assess for chromosomal structural rearrangements and identify embryos that may be unsuitable for use in assisted reproductive procedures.

Chromosomal structural rearrangements include:

• dIslocations
• translocations
• inversions
• deletion
• duplications

If the chromosomal set is complete the structural rearrangement is known as balanced. Where there is missing or extra chromosomal information the structural rearrangement is known as unbalanced.

Chromosomal structural rearrangements (particularly deletions and duplications) can cause significant genetic abnormalities or disease. However, many balanced structural rearrangements do not have an immediate effect but can impact on the carrier’s ability to conceive.

PGT-SR may be used where there is a known structural relocation in the gamete provider.

Approval for PGT-SR is required from the Reproductive Technology Council.

'Sex selection' refers to a genetic test that checks embryonic cells, collected via IVF, to identify embryos of a particular sex which are then considered for transfer.

Sex selection may only be approved to avoid the transmission of a sex-linked genetic abnormality or disease.

Sex selection for non-medical reasons, such as family balancing, is prohibited in Western Australia.

Approval for medical sex selection is required from the Reproductive Technology Council.

The term 'saviour sibling' refers to the use of preimplantation genetic testing (PGT) in conjunction with human leukocyte antigen typing to select an embryo, created through IVF, that is able to provide tissue or stem cells to treat a life threating medical condition in a sibling.

To access to PGT for this purpose a person must have:

• A medical or genetic reason to access IVF and
• A risk of genetic condition in the embryo.