Preimplantation Genetic Testing (PGT)
What Is Preimplantation Genetic Testing?
Preimplantation Genetic Testing (PGT) is a genetic testing approach used during IVF to examine embryos for specific genetic or chromosomal findings before an embryo is selected for transfer to the uterus. It can provide additional genetic information to support reproductive decision-making as part of an IVF treatment pathway.
Depending on the clinical situation, Preimplantation Genetic Testing may be used to look for specific inherited genetic conditions or certain chromosomal abnormalities. The appropriate type of PGT depends on factors such as family history, known genetic variants and the reason for testing.
PGT does not replace genetic counselling or other recommended assessments. A qualified genetics professional can help explain whether testing may be appropriate and what the results may mean for the individual or couple.
What Can Preimplantation Genetic Testing Identify?
Preimplantation Genetic Testing can examine embryos for certain genetic or chromosomal findings before embryo transfer. What is assessed depends on the type of PGT and the specific genetic or reproductive concern.
| What May Be Identified | What It Means |
|---|---|
| Specific inherited genetic conditions | Certain genetic variants associated with a known inherited condition may be assessed when there is a specific family or genetic risk. |
| Chromosomal abnormalities | Some PGT approaches can assess embryos for specific chromosome number abnormalities, depending on the clinical indication. |
| Structural chromosome changes | In appropriate cases, testing can assess embryos for chromosome changes related to a known parental structural rearrangement. |
| Known familial genetic variants | Where a specific disease-causing variant is known in a family, targeted embryo testing may be considered as part of an IVF pathway. |
The findings that can be assessed depend on the type of PGT and the individual clinical situation. Genetic counselling can help clarify which testing approach may be appropriate and what the results may mean.
How Does Preimplantation Genetic Testing Work?
Preimplantation Genetic Testing is carried out as part of an IVF treatment cycle. Eggs are collected and fertilised in the laboratory to create embryos, which are allowed to develop for several days before genetic testing is performed.
A small sample of cells is taken from an embryo and sent to a specialist laboratory for genetic analysis. The embryos are then assessed according to the specific genetic or chromosomal findings being investigated.
The results can provide additional information to help the fertility and genetics team determine which embryos may be suitable for consideration for transfer. The process and testing approach depend on the individual’s genetic circumstances and the type of PGT being considered.
What Are the Different Types of Preimplantation Genetic Testing?
Different types of Preimplantation Genetic Testing are used for different genetic or chromosomal concerns. The appropriate approach depends on the individual's reproductive and genetic circumstances.
PGT-M
Preimplantation Genetic Testing for Monogenic disorders (PGT-M) can be used to test embryos for a specific inherited condition caused by a known genetic variant.
PGT-A
Preimplantation Genetic Testing for Aneuploidy (PGT-A) assesses embryos for abnormalities in chromosome number.
PGT-SR
Preimplantation Genetic Testing for Structural Rearrangements (PGT-SR) can assess embryos when a parent has a known structural chromosome rearrangement.
Each type of PGT addresses a different genetic question. Genetic counselling can help determine which approach may be relevant based on family history, genetic findings and reproductive circumstances.
Who May Consider Preimplantation Genetic Testing?
Preimplantation Genetic Testing may be considered by individuals or couples undergoing IVF who have a known or suspected genetic or chromosomal risk that could affect their embryos.
This may include people with a known inherited genetic condition in the family, a known genetic variant, or a parental chromosome rearrangement. PGT may also be discussed in some reproductive situations where assessment of embryo chromosomes is considered appropriate.
Whether PGT is suitable depends on the individual clinical and genetic circumstances. Genetic counselling can help review family history, previous genetic results and reproductive goals before deciding whether further testing should be considered.
When Is Preimplantation Genetic Testing Performed During IVF?
Preimplantation Genetic Testing is performed during an IVF cycle before an embryo is selected for transfer. The testing takes place after embryos have developed in the laboratory and before embryo transfer.
| IVF Stage | Role of Preimplantation Genetic Testing |
|---|---|
| Egg collection and fertilisation | Eggs are collected and fertilised in the laboratory to create embryos as part of the IVF cycle. |
| Embryo development | Embryos develop in the laboratory for several days before a suitable sample can be collected for genetic analysis. |
| Embryo biopsy and genetic analysis | A small sample of cells is taken from an embryo and analysed according to the specific type of PGT being performed. |
| Before embryo transfer | The genetic findings provide additional information that may help inform which embryos are considered for transfer. |
Preimplantation Genetic Testing takes place before embryo transfer. The exact timing and laboratory process can vary depending on the type of PGT and the individual IVF treatment plan.
What Is the Preimplantation Genetic Testing Process?
The Preimplantation Genetic Testing process begins with an IVF cycle, followed by embryo development in the laboratory. Once embryos reach the appropriate stage, a small number of cells can be collected from an embryo for genetic analysis.
The embryo sample is analysed in a specialist laboratory using the testing approach selected for the individual’s genetic or chromosomal concern. The embryo itself is not routinely tested as a whole; instead, the laboratory analyses the cells collected during the biopsy.
The genetic results are then reviewed alongside the individual’s clinical and reproductive circumstances. Where appropriate, the findings can help the fertility team consider which embryos may be suitable for transfer as part of the IVF pathway.
The specific process can vary depending on the type of PGT, the genetic question being investigated and the laboratory involved. Genetic counselling can help explain the testing process, possible findings and their limitations.
How Is Embryo Testing Used Before Embryo Transfer?
Embryo testing provides additional genetic information before an embryo is considered for transfer during an IVF cycle.
Embryo Biopsy
- A small sample of cells is collected from an embryo at the appropriate stage of development.
- The embryo can be preserved while the genetic analysis is carried out.
Genetic Analysis
- The sample is analysed using the appropriate type of Preimplantation Genetic Testing.
- The analysis focuses on the specific genetic or chromosomal concern being investigated.
Results Review
- The genetic findings are reviewed alongside the individual's clinical and reproductive circumstances.
- The results can provide additional information about the embryos tested.
Embryo Transfer Planning
- The findings may help the fertility team consider which embryos are suitable for transfer.
- The final decision depends on the PGT results, clinical circumstances and the overall IVF treatment plan.
What Are the Potential Benefits and Limitations of Preimplantation Genetic Testing?
Preimplantation Genetic Testing can provide additional genetic information about embryos before embryo transfer. This may help individuals and couples make more informed reproductive decisions, particularly when there is a known inherited condition or chromosomal concern.
One potential benefit is the ability to identify embryos with certain genetic or chromosomal findings before transfer. Depending on the clinical situation, this may help the fertility and genetics team plan the next stage of treatment.
However, PGT also has limitations. It does not assess every possible genetic or health condition, and the results may not provide a complete picture of an embryo’s future health. Testing also involves embryo biopsy and laboratory analysis, and not every IVF cycle will produce embryos suitable for testing or transfer.
The significance of PGT results depends on the type of testing performed and the individual circumstances. Genetic counselling can help explain the potential benefits, limitations and uncertainties before testing is undertaken.
What Happens After Preimplantation Genetic Testing?
After Preimplantation Genetic Testing, the laboratory results are reviewed to provide information about the embryos tested. The next steps depend on the type of PGT, the findings and the individual's IVF treatment plan.
| Stage | What Happens |
|---|---|
| PGT results | The specialist laboratory provides a report describing the genetic or chromosomal findings identified through the testing performed. |
| Results interpretation | The findings are considered in the context of the type of PGT, the individual's genetic circumstances and the IVF treatment plan. |
| Embryo selection | Where appropriate, the results provide additional information that may help the fertility team consider which embryos are suitable for transfer. |
| Next steps | The fertility team discusses the available options and plans the next stage of treatment based on the PGT findings and the overall clinical circumstances. |
PGT results provide additional information rather than a guarantee of outcome. Their interpretation should take into account the specific test performed, the clinical context and any relevant genetic counselling.
Is Preimplantation Genetic Testing Right for Everyone?
Preimplantation Genetic Testing is not suitable or necessary for everyone undergoing IVF. Its potential value depends on the individual’s genetic circumstances, reproductive history and the specific reason for considering embryo testing.
PGT may be discussed when there is a known inherited genetic condition, a relevant genetic finding, a parental chromosome rearrangement or another clinical reason for considering embryo testing. However, the availability and suitability of a particular type of PGT depend on the circumstances and the testing requirements.
A genetics professional can review your family history, previous genetic results and reproductive plans to help determine whether PGT may be appropriate. This can also help you understand the potential benefits, limitations and alternatives before making a decision.
What Questions Should You Ask About Preimplantation Genetic Testing?
Before considering Preimplantation Genetic Testing, it can be helpful to discuss the purpose of testing, the type of PGT being considered and what the results may mean for your IVF treatment.
- Why might Preimplantation Genetic Testing be considered in my circumstances?
- Which type of PGT is appropriate for the genetic or chromosomal concern being investigated?
- What can the proposed testing identify, and what can it not identify?
- How might the results affect the options available for embryo transfer?
- What are the limitations or uncertainties associated with the test?
- Would genetic counselling be recommended before or after testing?
Understanding these points can help you make an informed decision about whether PGT fits your reproductive and genetic circumstances.
Frequently Asked Questions About Preimplantation Genetic Testing
What is Preimplantation Genetic Testing?
Preimplantation Genetic Testing (PGT) is a genetic testing approach used during IVF to examine embryos for certain genetic or chromosomal findings before an embryo is considered for transfer.
What are the main types of PGT?
The main types are PGT-M, which assesses embryos for specific monogenic inherited conditions; PGT-A, which assesses chromosome number; and PGT-SR, which is used when a parent has a known structural chromosome rearrangement.
Does PGT test for all genetic conditions?
No. PGT does not identify every possible genetic condition or health problem. The findings that can be assessed depend on the type of testing and the specific genetic question being investigated.
Does Preimplantation Genetic Testing guarantee a healthy baby?
No. PGT can provide additional genetic information about embryos, but it cannot guarantee a particular pregnancy or health outcome. Other factors may also affect pregnancy and a child’s health.
Is PGT performed before or after embryo transfer?
PGT is performed before embryo transfer. A sample of cells is taken from an embryo and analysed in a specialist laboratory before the fertility team considers the next steps.
Is Preimplantation Genetic Testing suitable for everyone having IVF?
No. PGT is not necessary or appropriate for everyone undergoing IVF. Its potential value depends on the individual’s genetic and reproductive circumstances and the reason for considering embryo testing.
Do I need genetic counselling before PGT?
Genetic counselling may be recommended, particularly when PGT is being considered because of a known inherited condition, genetic finding or chromosome rearrangement. It can help explain the testing options, limitations and possible implications of the results.
Can PGT be used when there is a genetic condition in the family?
It may be possible when the specific genetic condition or variant can be identified and the appropriate testing approach can be developed. The suitability of PGT depends on the particular condition and individual circumstances.
Preimplantation Genetic Testing at London Genetics
Deciding whether Preimplantation Genetic Testing is appropriate involves understanding your genetic circumstances, reproductive history and the specific reason for considering embryo testing.
Personalised Genetic Assessment
At London Genetics, we consider relevant family history, previous genetic results and reproductive circumstances when discussing PGT. This helps identify whether genetic testing may be appropriate and which type of PGT may be relevant.
Understanding Your Options
PGT can involve complex genetic information and has important limitations. We can help you understand what the proposed testing may identify, what the results may mean and how the findings may inform discussions with your fertility team.
If you are considering Preimplantation Genetic Testing because of an inherited condition, genetic finding or other reproductive concern, a consultation can provide an opportunity to discuss your circumstances and available options.
Considering PGT? Arrange a consultation with London Genetics to discuss whether Preimplantation Genetic Testing may be appropriate for your circumstances.
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