What is PGT-A (Preimplantation Genetic Testing for Aneuploidy)?

Preimplantation Genetic Testing for Aneuploidy (PGT-A) is an advanced screening technique used during in vitro fertilisation (IVF) to evaluate embryos for chromosomal abnormalities. Aneuploidy refers to an irregular number of chromosomes, which can result in failed implantation, miscarriage, or genetic disorders. PGT-A is designed to identify embryos with the correct number of chromosomes, increasing the likelihood of a successful pregnancy and reducing the risk of genetic complications.

PGT-A is not a diagnostic test for specific genetic conditions but rather a broad screening tool to ensure chromosomal normality. This technique is particularly beneficial for individuals experiencing recurrent miscarriages, couples with a history of failed IVF cycles, or those undergoing treatment at an advanced maternal age when chromosomal abnormalities are more common.

How does it work?

PGT-A works by analysing cells from an embryo created during an IVF cycle. The process begins with the fertilisation of an egg by sperm in the laboratory. Once the embryo reaches the blastocyst stage, typically five to seven days after fertilisation, a few cells are carefully removed from the outer layer of the embryo, known as the trophectoderm. This biopsy does not harm the embryo's potential to develop.

The extracted cells are then subjected to genetic analysis, where scientists examine the chromosomal makeup. Using advanced techniques, such as next-generation sequencing (NGS), the laboratory can detect chromosomal abnormalities, including missing or extra chromosomes. Embryos identified as chromosomally normal, or euploid, are prioritised for transfer to the uterus.

What's involved in PGT-A?

PGT-A is integrated into an IVF treatment cycle and involves several steps:

1. Ovarian stimulation: The patient undergoes hormonal treatment to stimulate the ovaries to produce multiple eggs.
2. Egg retrieval: Mature eggs are collected from the ovaries using a minimally invasive procedure under ultrasound guidance.
3. Fertilisation: The eggs are fertilised with sperm in the laboratory, either through conventional IVF or intracytoplasmic sperm injection (ICSI).
4. Embryo development: The embryos are cultured and monitored for growth and quality until they reach the blastocyst stage.
5. Embryo biopsy: A small number of cells are removed from the trophectoderm for genetic testing.
6. Genetic analysis: The biopsied cells are sent to a specialised laboratory for chromosomal analysis.
7. Embryo transfer: A euploid embryo is selected and transferred to the uterus during a fresh or frozen embryo transfer cycle.

How can I prepare for PGT-A?

Preparation for PGT-A involves standard IVF readiness steps, as the testing is an extension of an IVF treatment. Patients should follow the recommendations of their fertility specialist, which may include:

• Undergoing a thorough evaluation of reproductive health, including hormonal assessments and ultrasound scans.
• Optimising general health through a balanced diet, regular exercise, and avoiding smoking and excessive alcohol consumption.
• Discussing the benefits and limitations of PGT-A with their specialist to set realistic expectations.
• Understanding the financial and time commitments involved, as PGT-A is an additional procedure within the IVF cycle.

What happens after PGT-A?

After the genetic analysis is completed, the results are provided to the fertility specialist, who will discuss them with the patient. The embryos will be categorised as euploid (chromosomally normal), aneuploid (chromosomally abnormal), or, in some cases, mosaic (a mix of normal and abnormal cells).

Euploid embryos are prioritised for transfer, as they have the highest potential for successful implantation and a healthy pregnancy. Mosaic embryos may also be considered for transfer under certain circumstances, but this decision is made on a case-by-case basis. Aneuploid embryos are not usually recommended for transfer due to their low likelihood of success and increased risk of complications.

Embryos not immediately transferred can be frozen for future use. The patient may proceed with a fresh transfer or opt for a frozen embryo transfer in a later cycle, depending on the timing and their individual treatment plan.

How does PGT-A assist in fertility? Does it help to improve success rates?

PGT-A can improve the success rates of IVF by ensuring that only chromosomally normal embryos are selected for transfer. This can result in higher implantation rates, reduced miscarriage rates and shorter timeframes to achieve a successful pregnancy. By identifying embryos with the best chance of developing into a healthy baby, PGT-A allows fertility specialists to personalise treatment and optimise outcomes.

PGT-A is particularly beneficial for:

• Patients experiencing recurrent pregnancy loss.
• Women of advanced maternal age, where the risk of chromosomal abnormalities increases.
• Couples with a history of failed IVF cycles.
• Patients wishing to minimise the risk of transferring embryos with chromosomal abnormalities.

While PGT-A does not guarantee pregnancy, it significantly enhances the likelihood of a positive outcome in appropriate cases.
 

Is PGT-A safe?

PGT-A is considered a safe and well-established procedure when performed by experienced specialists. The embryo biopsy is minimally invasive and has been shown not to significantly affect the embryo's viability. Advances in technology, such as next-generation sequencing, have improved the accuracy and reliability of genetic analysis.

However, as with any medical procedure, there are some risks. These may include:

• A small chance of damage to the embryo during the biopsy process.
• The possibility of inconclusive or unclear results, particularly with mosaic embryos.
• The emotional and financial implications of discovering that no embryos are suitable for transfer.

It’s important for patients to discuss the risks and benefits of PGT-A with their fertility specialist to make an informed decision about their treatment.

Which specialist performs PGT-A?

PGT-A is performed as part of an IVF treatment cycle and involves a multidisciplinary team of specialists. The process is overseen by a fertility specialist, who manages the patient's treatment plan and coordinates the necessary steps. The embryologist plays a key role in handling the embryos, performing the biopsy, and preparing the cells for genetic analysis.

The genetic testing itself is carried out in a specialised laboratory by geneticists and technicians experienced in analysing chromosomal abnormalities. The fertility specialist then reviews the results and provides guidance on the next steps in the treatment process.

Patients undergoing PGT-A should choose a clinic with expertise in IVF and genetic testing to ensure the highest standards of care and accuracy.