Visual communication aid: Preimplantation genetic testing (PGT)

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• Preimplantation genetic testing (PGT)

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More information about these and other VCAs is available in this article.

Preimplantation genetic testing (PGT), is a type of fertility treatment that may be an option for people who have a personal or family history of a genetic condition. There are different types of PGT. This information is most relevant for PGT-M and PGT-SR (see ‘Key phrases’).​

PGT involves testing embryos, created through in vitro fertilisation (IVF), to find out which ones have inherited a specific genetic change or changes that are known to cause a genetic condition. Only unaffected embryos are then used to try to start a pregnancy. For PGT-M or PGT-SR to be possible, the genetic change(s) that causes the condition in the family must be known.

The process for PGT is as follows:

1. Eggs and sperm are combined in the lab to create embryos.​
2. Embryos grow for 5–7 days.
3. A few cells are taken from each embryo – these cells contain the genetic material (DNA).​
4. Embryos are then frozen.​
5. DNA from each embryo is tested. The testing process depends on the type of genetic change and DNA samples may also be needed from the parents or other family members.​
6. Results show which embryos have inherited the genetic change(s)​ and which have not.
7. One unaffected embryo is transferred to the womb to try to start a pregnancy.​

In the UK, a condition must have a PGT licence from the Human Fertilisation and Embryology Authority (HFEA) before testing can be offered.​

There are also eligibility criteria for NHS-funded PGT. Referrals for PGT must be made by an NHS clinical genetics service.​

Figure 1: Diagram showing the steps of PGT
(View larger size)

• ​PGT-M (monogenic): Testing for a change(s) in a single gene that causes a specific condition.​
• ​PGT-SR (structural rearrangement): Testing for chromosome changes, such as translocations.

For patients

• Human Fertilisation and Embryology Authority (HFEA): Pre-implantation genetic testing for monogenic disorders (PGT-M) and Pre-implantation genetic testing for chromosomal structural rearrangements (PGT-SR)
• ​NHS Guy’s and St Thomas’ NHS Foundation Trust: Pre-implantation genetic testing (PGT-M/SR)