Preimplantation Genetic Testing (PGT)

What is PGT?

Preimplantation genetic testing (PGT) examines embryos during IVF before transfer to identify any potential genetic or chromosomal issues. The goal is to select the healthiest embryos, improving the chances of a successful pregnancy and reducing the risk of passing on genetic disorders.

It’s often recommended for people with a known inherited genetic condition, a chromosome rearrangement, or who have experienced recurrent miscarriage or previous unsuccessful IVF treatment. It can help identify embryos with the best chance of implantation, but it does not guarantee pregnancy or rule out every possible health issue.

Who should consider PGT?

PGT may be helpful if you have:

Concerns about passing on single gene mutations
If you or your partner carry a known inherited gene change, PGT may help identify embryos that have not inherited the condition before transfer.
A chromosome rearrangement (translocation)
If one partner carries a balanced translocation or other chromosome rearrangement, PGT can help assess whether embryos have a normal or balanced chromosome pattern.
Had a previous pregnancy affected by chromosomal variation
PGT may be considered if you have had a pregnancy or child affected by a chromosomal condition, as it can help reduce the chance of the same issue occurring again.
An increased risk of passing on a genetic disorder due to advanced maternal age (usually over 35)
As egg quality and chromosomal stability can decline with age, PGT may be discussed to help identify embryos with a lower risk of chromosomal abnormalities.
Experienced recurrent miscarriage
If you have had two or more miscarriages, PGT may help determine whether chromosome issues in the embryos could be contributing to pregnancy loss.
Experienced repeated unsuccessful IVF cycles
If multiple good-quality embryos have been transferred without a resulting pregnancy, PGT may help identify whether embryo chromosome issues are affecting implantation.
Unexplained infertility
When no clear cause of infertility has been found, PGT may sometimes be used as part of a broader IVF plan to help select embryos with the best chance of success.

Types of PGT and what they test for

PGT-A (PGT for aneuploidy)

Checks embryos for the correct number of chromosomes. It can help identify embryos with extra or missing chromosomes, which may be linked to implantation problems, miscarriage, or conditions such as Down syndrome.

PGT-M (PGT for monogenic conditions)

Checks for a known inherited gene change linked to specific conditions, such as cystic fibrosis, Huntington’s disease, sickle cell disease, Duchenne muscular dystrophy, thalassaemia, Tay-Sachs or Fragile X.

PGT-SR (PGT for structural rearrangements)

Checks embryos for structural chromosome rearrangements, such as translocations or inversions. Carriers are often healthy, but embryos may inherit unbalanced chromosome material, which can increase the risk of miscarriage or chromosomal abnormalities.

How does PGT work?

PGT is carried out after a standard IVF cycle, once the embryos have grown in the laboratory for about five days. At this stage, a small number of cells are removed from each embryo in a procedure called an embryo biopsy, and the sample is then tested for genetic abnormalities. The embryos that are found to be healthy or unaffected are then chosen for embryo transfer, helping improve the chance of a successful pregnancy in the right circumstances.

More about IVF

How accurate is PGT and when are the results available?

PGT provides detailed information about an embryo’s chromosomes or specific gene changes, but no test is 100% accurate, so prenatal testing is still recommended during pregnancy.

Results are usually available several days after the embryo biopsy, while the embryos remain safely frozen. Once the testing is complete, Dr Ritu will discuss which embryos are suitable for transfer and whether any could be stored for future transfers.

FAQs about PGT

What are the risks and limitations of PGT?

PGT has a small risk (~5%) of embryo damage during biopsy and is not 100% accurate, so prenatal testing like amniocentesis is still recommended during pregnancy. Not all embryos may be suitable for transfer after testing, though there are no documented increased health risks for children born after undertaking PGT.

What are the benefits of PGT?

PGT helps identify embryos with genetic abnormalities before transfer, reducing the risk of miscarriage and inherited genetic conditions. It increases the chances of a successful pregnancy, especially for women over 35 or those with recurrent miscarriages, and allows couples who carry known genetic disorders to avoid passing them on to their children. This can lead to healthier babies and fewer emotionally and financially draining unsuccessful IVF cycles.

What’s the difference between PGT and IVF?

IVF is the treatment process used to help with conception, where eggs are collected, fertilised in the laboratory, and embryos are created. PGT is an additional test that can be done during IVF to check embryos for certain genetic or chromosomal issues before transfer. In other words, IVF helps create embryos, while PGT helps identify which embryos may be the most suitable for transfer.

Should everyone undergo PGT?

PGT is not suitable for everyone and may be useful when there is a known genetic condition, a history of recurrent miscarriage, or previous unsuccessful IVF cycles. Dr Ritu can help determine whether PGT is appropriate based on your medical history, fertility goals, and individual circumstances.

Preimplantation Genetic TestingGive yourself peace of mind and the ability to make informed decisions